hypothesis on plastic pollution

Loading metrics

Open Access

Confronting plastic pollution to protect environmental and public health

* E-mail: [email protected] (LG); [email protected] (JE)

Affiliation Public Library of Science, San Francisco, California, United States of America

Affiliation Center for the Advancement of Public Action, Bennington College; Beyond Plastics, Bennington, Vermont, United States of America

• Liza Gross, 
• Judith Enck

Published: March 30, 2021

• https://doi.org/10.1371/journal.pbio.3001131
• Reader Comments

A new collection of evidence-based commentaries explores critical challenges facing scientists and policymakers working to address the potential environmental and health harms of microplastics. The commentaries reveal a pressing need to develop robust methods to detect, evaluate, and mitigate the impacts of this emerging contaminant, most recently found in human placentas.

Citation: Gross L, Enck J (2021) Confronting plastic pollution to protect environmental and public health. PLoS Biol 19(3): e3001131. https://doi.org/10.1371/journal.pbio.3001131

Copyright: © 2021 Gross, Enck. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The authors received no specific funding for this work.

Competing interests: Liza Gross is a current paid employee of the Public Library of Science.

The explosive production of affordable plastic goods during the 1950s ushered in an era of disposable living, fueled by an addiction to convenience and consumerism, that has created one of the world’s most vexing pollution problems. Plastic, for all its uses, has left a trail of debris from the deepest ocean trenches to the remotest polar reaches. Plastic pollutes throughout its life cycle, from its beginnings as a by-product of greenhouse gas-emitting oil and natural gas refining to its degradation-resistant end as increasingly fragmented shards of micro-and nanoplastics in atmospheric currents, alpine snow, estuaries, lakes, oceans, and soils. Researchers are finding microplastics in the gut or tissue of nearly every living thing they examine, including the placentas of unborn children.

The first sign of this burgeoning crisis came nearly half a century ago, when marine biologists first spotted tiny plastic pellets stuck to tiny marine organisms and seaweed in the North Atlantic’s Sargasso Sea. Describing their discovery in 1972, the scientists predicted, presciently, that “increasing production of plastics, combined with present waste disposal practices, will probably lead to greater concentrations on the sea surface” [ 1 ].

Researchers have struggled to keep tabs on plastic production and waste ever since. The first global assessment of mass-produced plastics, reported in 2017, estimated that manufacturers had produced 8,300 million metric tons of virgin plastics, creating 6,300 million metric tons of plastic waste—with only 9% recycled, 12% incinerated, and the rest either piling up in landfills or entering the environment [ 2 ].

Some 15 million metric tons of plastic enters the oceans every year [ 3 ], choking marine mammals, invading the guts of fish and seabirds, and posing unknown risks to the animals, and people, who eat them. Plastics release toxic chemicals added during manufacturing as they splinter into smaller and smaller fragments, with half-lives ranging from 58 to 1,200 years [ 4 ]. Persistent organic pollutants have a high affinity for plastic particles, which glom on to these contaminants as do pathogens in the ocean, presenting additional risks to marine life and the food web. Scientists once viewed freshwater lakes and rivers as primarily conduits for plastic, delivering trash from land to the sea, but now realize they’re also repositories.

Plastic production increased from 2 million metric tons a year in 1950 to 380 million metric tons by 2015 and is expected to double by 2050 [ 2 ]. Petrochemical companies’ embrace of fracking has exacerbated the crisis by producing large amounts of ethane, a building block for plastic.

Recognizing the scope and urgency of addressing the plastic pollution crisis, PLOS Biology is publishing a special collection of commentaries called “Confronting plastic pollution to protect environmental and public health.”

In commissioning the collection, we aimed to illuminate critical questions about microplastics’ effects on environmental and human health and explore current challenges in addressing those questions. The collection features three evidence-based commentaries that address gaps in understanding while flagging research priorities for improving methods to detect, evaluate, and mitigate threats associated with this emerging contaminant.

Environmental ecotoxicologist Scott Coffin and colleagues address recent government efforts to assess and reduce deleterious effects of microplastics, which challenge traditional risk-based regulatory frameworks due to their particle properties, diverse composition, and persistence. In their Essay, “Addressing the environmental and health impacts of microplastics requires open collaboration between diverse sectors” [ 5 ], the authors use California as a case study to suggest strategies to deal with these uncertainties in designing research, policy, and regulation, drawing on parallels with a similar class of emerging contaminants (per- and polyfluoroalkyl substances).

In “Tackling the toxics in plastics packaging” [ 6 ], environmental toxicologist Jane Muncke focuses on a major driver of the global plastic pollution crisis: single-use food packaging. Our throwaway culture has led to the widespread use of plastic packaging for storing, transporting, preparing, and serving food, along with efforts to reduce plastic waste by giving it new life as recycled material. But these efforts ignore evidence that chemicals in plastic migrate from plastic, making harmful chemicals an unintentional part of the human diet. Addressing contamination from food packaging is an urgent public health need that requires integrating all existing knowledge, she argues.

Much early research on microplastics focused on ocean pollution. But the ubiquitous particles appear to be interfering with the very fabric of the soil environment itself, by influencing soil bulk density and the stability of the building blocks of soil structure, argue Matthias Rillig and colleagues in their Essay. Microplastics can affect the carbon cycle in numerous ways, for example, by being carbon themselves and by influencing soil microbial processes, plant growth, or litter decomposition, the authors argue in “Microplastic effects on carbon cycling processes in soils” [ 7 ]. They call for “a major concerted effort” to understand the pervasive effects of microplastics on the function of soils and terrestrial ecosystems, a monumental feat given the immense diversity of the particles’ chemistry, aging, size, and shape.

The scope and effects of plastic pollution are too vast to be captured in a few commentaries. Microplastics are everywhere and researchers are just starting to get a handle on how to study the influence of this emerging contaminant on diverse environments and organisms. But as the contributors to this collection make clear, the pervasiveness of microplastics makes them nearly impossible to avoid. And the uncertainty surrounding their potential to harm people, wildlife, and the environment, they show, underscores the urgency of developing robust tools and methods to understand how a material designed to make life easier may be making it increasingly unsustainable.

• View Article
• PubMed/NCBI
• Google Scholar

When you choose to publish with PLOS, your research makes an impact. Make your work accessible to all, without restrictions, and accelerate scientific discovery with options like preprints and published peer review that make your work more Open.

• PLOS Biology
• PLOS Climate
• PLOS Complex Systems
• PLOS Computational Biology
• PLOS Digital Health
• PLOS Genetics
• PLOS Global Public Health
• PLOS Medicine
• PLOS Mental Health
• PLOS Neglected Tropical Diseases
• PLOS Pathogens
• PLOS Sustainability and Transformation
• PLOS Collections
• About This Blog
• About PLOS ONE
• Official PLOS Blog
• EveryONE Blog
• Speaking of Medicine
• PLOS Biologue
• Absolutely Maybe
• DNA Science
• PLOS ECR Community
• All Models Are Wrong
• About PLOS Blogs

Understanding Plastic Pollution: The potential health effects, abundance and classification of microplastics

PLOS ONE recently published a new Collection of research entitled Recent Advances in Understanding Plastic Pollution . Given the broad scope of this collection, and the potential implications this research has on both humans the rest of the biosphere globally, we are digging deeper into the findings with some of the authors from papers included in this collection. In this third installment of interviews, we learn more about how microplastics may affect metabolism, and how it is getting easier to use machine learning to analyse samples containing microplastics.

CJ O’Brien, Plastics Campaign Associate, Oceana

CJ O’Brien has worked in research and advocacy to protect the ocean from plastic pollution in the United States and Zanzibar, Tanzania. She is currently the Plastics Campaign Associate at Oceana where she works on policies to reduce the production and use of single-use plastic. Before joining Oceana, she earned a master’s degree in Development Practice from Emory University with a focus on Environmental Conservation and Monitoring and Evaluation (M&E). There, she grappled with the complex interactions between marine conservation, plastic pollution, and international development. CJ also has a B.S. in Biology from California Lutheran University. Her honors thesis explored the impacts of plastic on the digestive enzyme activity in marine mussels which is the study highlighted here.

CJ O’Brien’s paper in this collection: O’Brien CJ, Hong HC, Bryant EE, Connor KM (2021) The observation of starch digestion in blue mussel  Mytilus galloprovincialis  exposed to microplastic particles under varied food conditions. PLoS ONE 16(7): e0253802. https://doi.org/10.1371/journal.pone.0253802

PLOS: In this paper, you studied the effects of microplastics on blue mussel Mytilus galloprovincialis during different food regimes. Why is this species particularly interesting to study in order to understand plastic pollution?

CJO: Mytilus galloprovincialis are small but mighty in their importance to the marine ecosystem and to plastic pollution research. Many researchers study this species because they are bioindicators which means they help us monitor the overall health of the environment. Mytilus galloprovincialis filter feed and are sessile creatures, making them extremely sensitive to pollution and other anthropogenic changes. Studying this species and its physiological reaction to the exposure of microplastic allowed us as researchers to get a better look at how microplastics are not only impacting them as a species, but how microplastic might be impacting the ecosystem as a whole. 

Additionally, Mytilus galloprovincialis are crucial to the marine environment and to humans as well. This species is constantly filtering the water column in which they live, creating more clean environments for their marine neighbors. They are also found all over the world and are cultivated for food in many different regions. Not to mention they make great lab subjects as they are easy to care for. I would say that intertidal filter feeders in general are extremely fascinating organisms and crucial in our understanding of plastic pollution, the health of the ocean, and the health of humans. 

PLOS: You found that enzyme activity was affected by the presence of microplastics in the high-food regime only. Was this a result you had foreseen? How is the high-food regime reflected in the real lives of this species?

CJO: This outcome was shocking to me. I expected amylase activity to be negatively affected by the presence of microplastic in both feeding regimes. I thought that since microplastic holds no nutrition for these organisms, that filtering microplastic particles would take up a large proportion of their energy to filter, increase toxicity, or reduce available organic content available for digestion. Theoretically, these perturbations could hinder their ability to make or secrete amylase and survive. However, mussels evolved a range of digestive related characteristics to cope with fluctuations in nutrients and understanding how they modulate them when exposed to microplastic pollution is an emerging field of science.

In our experiment, we subjected mussels to fluctuating feeding environments that differ, similar to that to mussels at different shore levels. Mussels fed high food concentrations represented mussels that live lower in the water column and are exposed to more feeding options than mussels high on the shore due to daily tidal variation. With that context, I thought that the amylase activity in mussels in the low food group would be impacted more than mussels in the high food group. This inference was not observed and in fact high microplastics led to unpredictably high amylase activity.

This was interesting to me because food digestion is positively related to food abundance–the digestive modulation hypothesis–and microplastics is not food. Mussels are adapted to conserve energy as much as they can due to unpredictable environments, such as tidal, thermal, and pH variation. Any change to their energy reserves in nature could impact their growth, survival, and fitness. However, our study showed that it is possible that even under very high microplastic exposures and presumably less organic content ingested, amylase activity was actually increased to compensate for diluted food. 

PLOS: Working to combat plastic pollution must be endlessly inspiring but occasionally daunting. What motivated you to work in this field, and what are the rewards that keep you going?

CJO: Growing up in Florida, I’ve always had a deep curiosity and connection to the ocean. My motivation for getting into this field was fueled by wanting to protect the place that I loved most. I increasingly saw plastic pollution on beaches that I spent time at and as I started to learn more, I realized just how big this problem is. I was utterly fascinated that a man-made material, made to last forever but oftentimes only used for a few moments has caused so much harm–especially microplastic which can be microscopic. It is so insidious!

Currently, I work on policies that reduce the production and use of single-use plastic. While I don’t work in research anymore, I’ve seen firsthand how research influences policies that reduce single-use plastic. It is so crucial that researchers continue to investigate how this pollutant impacts the health of our oceans and the health of us as humans. Plastic production is expected to increase and if we are to have any chance in fighting the plastic pollution crisis, we will need all hands on deck from scientists, policymakers, as well as artists, musicians, community members, and young people. I feel hopeful when I see collaborative, creative, and equitable approaches to this problem.

PLOS: Several other studies in this Collection also look the effects of plastic pollution on living species. Has seeing these other research studies in the collection helped inspire any thoughts about future work you might do, or other advances your research community will make?

CJO: Our study subjected mussels to high concentrations of spherical microplastics that may have an effect on mussels in future microplastics conditions. Our results showed that these types of microplastics are not lethal over short exposures. I continue to monitor studies of microplastics on bivalves and other marine organisms in general in my role as the Plastics Campaign Associate. The Connor Lab at University of California-Irvine continues to deeply study how bivalves work from genome to phenome.

Ho-min Park, PhD Student, Ghent University

Hello, my name is Ho-min Park. I am currently pursuing a doctoral degree in computer science engineering from Ghent University, Belgium. In this context, I am working as a teaching assistant for the Informatics and Bioinformatics courses at Ghent University Global Campus in Incheon, Korea. This extended campus of Ghent University offers educational programmes in Molecular Biotechnology, Food Technology, and Environmental Technology. As a dry lab scientist, I am conducting convergence-oriented research that applies artificial intelligence to predictive tasks that have been put forward by the different wet labs at Ghent University Global Campus.

Ho-min Park’s paper in this collection: Park H-m, Park S, de Guzman MK, Baek JY, Cirkovic Velickovic T, Van Messem A, et al. (2022) MP-Net: Deep learning-based segmentation for fluorescence microscopy images of microplastics isolated from clams. PLoS ONE 17(6): e0269449. https://doi.org/10.1371/journal.pone.0269449

PLOS: You studied various machine learning techniques for annotating microplastics from fluorescence microscopy images, which is very promising for reducing the time and effort it takes researchers to analyze microscopy images. How close are we to where machine learning can truly analyze microscopy images as well as a human can?

HP: I think we are getting very close. For quite a few image analysis and annotation efforts that take up a lot of time, I even believe that machine learning techniques are already better than humans, given that humans tend to suffer from visual fatigue rather quickly. Furthermore, when targeting high-speed and high-quality image analyses, the ideal approach will most likely consist of first having machine learning analyze an image of interest, and then ask a domain expert to validate the analysis performed.

However, we still need to obtain a better understanding of the inherent limitations of data-driven approaches. Human-made data often contain biases and errors, and where these biases and errors can propagate to machine learning models that were trained on these human-made data. For example, while annotating our microscopy images, we were able to spot several image blobs that made it hard for humans to determine whether these blobs were denoting microplastics or light bleed artifacts, and where such ambiguities typically also affect the training and decision-making capabilities of machine learning models.

PLOS: You made all data and code publicly available for the software you developed for this project. What motivated you to do this? Do you know whether other researchers have used your code or software, maybe not yet for this project, but perhaps for any other code you’ve made available in the past?

HP: In imaging of microplastics, the acquisition of data requires several steps, and where most of these steps can be considered time-consuming and labor intensive, especially when they involve chemical processes. In particular, to obtain a set of microscopy images, we had to collect numerous clam samples, subsequently digesting the proteins and lipids, staining the remaining microplastics pieces, and performing image capturing with a microscope. As a result, most studies only make available the amount and the type of microplastics, and not the original images. However, this makes it challenging for other researchers to cross-validate experimental methods and results. We therefore took the decision to open up our data and our software, thus making it easier for other researchers to build on top of our work. In this respect, we also plan to post an introductory article on our work to the Papers with Code platform in the near future. Finally, although our paper was published only recently, we already received several inquiries regarding the usage of our data and our software.

PLOS: For this paper, you had two collaborating institutions and three “first authors” who contributed equally. Can you tell us more about how this collaboration worked?

HP: The idea of building a machine learning tool first came about when Maria Krishna, who is a PhD student in Food Chemistry at Ghent University Global Campus, encountered difficulties in manually counting microplastics in the fluorescence images she collected. After discussing these difficulties with me (Maria Krishna knew about my computer vision research), and after encouragement from our doctoral advisors, we decided to experiment with a few images and a number of deep learning models. This required a lot of work, both on the chemistry side (for the acquisition of microplastics from shellfish until image collection) and on the machine learning side (for model training and development of the GUI). In this context, we received a lot of help from two student interns, Sanghyeon Park and Jiyeon Baek, with Sanghyeon even staying on for the entire duration of the project.

PLOS: As a researcher, how do you hope to inspire other researchers, and the general public, to focus on plastic pollution as a social issue? What are some ways in which researchers who do not work directly in this field can help?

HP: With increasingly better methodologies to quantify microplastics pollution, including computational methodologies that leverage machine learning, we believe it will be easier to raise awareness about the seriousness of the spread of microplastics, and where this increased awareness will hopefully trigger more research and development efforts. These research and development efforts could for instance target the creation of biodegradable plastics, the discovery and possible engineering of organisms that can break down microplastics, and a better understanding of the risks posed by microplastics and their impact on human health, and where the latter effort would be of high interest to law and policy makers.

Cover image:  Port of Dover , 2014 Beach Clean (CC-BY 2.0)

Disclaimer: Views expressed by contributors are solely those of individual contributors, and not necessarily those of PLOS.

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name and email for the next time I comment.

March 8 marks International Women’s Day 2024. To celebrate, we interviewed one of our female Academic Editors, Dr. Siaw Shi Boon, who…

I would strongly advice aspiring academics to align their goals, expertise and skillset with what drives them intrinsically. Swetavalli Raghavan February 11…

In celebration of World AIDS Day, we interviewed Section Editor Limin Mao, Associate Professor at the Centre for Social Research in Health…

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• My Account Login
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 26 July 2022

Plastic pollution fosters more microbial growth in lakes than natural organic matter

• Eleanor A. Sheridan   ORCID: orcid.org/0000-0001-7358-7816 1 , 2 ,
• Jérémy A. Fonvielle   ORCID: orcid.org/0000-0002-8077-2419 1 ,
• Samuel Cottingham 1 ,
• Yi Zhang 1 ,
• Thorsten Dittmar   ORCID: orcid.org/0000-0002-3462-0107 3 , 4 ,
• David C. Aldridge   ORCID: orcid.org/0000-0001-9067-8592 2 &
• Andrew J. Tanentzap   ORCID: orcid.org/0000-0002-2883-1901 1  

Nature Communications volume  13 , Article number:  4175 ( 2022 ) Cite this article

20k Accesses

59 Citations

784 Altmetric

Metrics details

• Biogeochemistry
• Water microbiology

Plastic debris widely pollutes freshwaters. Abiotic and biotic degradation of plastics releases carbon-based substrates that are available for heterotrophic growth, but little is known about how these novel organic compounds influence microbial metabolism. Here we found leachate from plastic shopping bags was chemically distinct and more bioavailable than natural organic matter from 29 Scandinavian lakes. Consequently, plastic leachate increased bacterial biomass acquisition by 2.29-times when added at an environmentally-relevant concentration to lake surface waters. These results were not solely attributable to the amount of dissolved organic carbon provided by the leachate. Bacterial growth was 1.72-times more efficient with plastic leachate because the added carbon was more accessible than natural organic matter. These effects varied with both the availability of alternate, especially labile, carbon sources and bacterial diversity. Together, our results suggest that plastic pollution may stimulate aquatic food webs and highlight where pollution mitigation strategies could be most effective.

Similar content being viewed by others

Microbial decomposition of biodegradable plastics on the deep-sea floor

Taku Omura, Noriyuki Isobe, … Tadahisa Iwata

Microplastics affect sedimentary microbial communities and nitrogen cycling

Meredith E. Seeley, Bongkeun Song, … Robert C. Hale

Polyethylene degradation and assimilation by the marine yeast Rhodotorula mucilaginosa

Annika Vaksmaa, Lubos Polerecky, … Helge Niemann

Introduction

The response of microbes to widespread and growing plastic pollution in freshwaters has consequences for ecosystem metabolism and food web health 1 , 2 , 3 . In addition to providing a substrate for biofilm colonisation 4 , plastics leach dissolved organic matter (DOM) during mechanical, photochemical, and biological degradation 5 , 6 , 7 . This plastic leachate can provide energy for bacterial growth 8 , 9 , and be transferred upwards through food webs to support the growth of higher trophic levels 10 . However, plastic leachate can also impair bacterial growth because of toxic compounds added to synthetic polymers during manufacturing, for example to increase plastic flexibility and heat stability 11 . As many of these toxic additives are hydrophobic organic compounds that tightly sorb to synthetic polymers, they can also harm, and potentially biomagnify in, higher trophic levels that ingest bacterial decomposers 2 . Determining the conditions in which bacteria can best grow, and consequently deplete plastic leachate from the environment, can ultimately help prioritise efforts to mitigate and clean-up global plastic pollution.

Few data exist on the molecular composition and fate of plastic leachate in freshwaters, especially compared with natural DOM. Synthetic polymers are generally regarded as non-biodegradable 12 , but plastics also contain many labile and potentially bioavailable additives—such as plasticizers, colourants, and antioxidants—that are used to give polymers their functional properties 13 , 14 , 15 . These additives can account for up to 70% of plastic debris on a per-mass basis 14 , 15 . The most common plastics, i.e. polyethylene and polypropylene 16 , 17 , are also buoyant and so undergo the highest rates of photodegradation and leaching in the warm, irradiated conditions of surface waters 9 . Consequently, plastic leachate can accumulate at high concentrations in surface waters relative to natural DOM 8 . If this leachate contains more labile compounds than natural DOM, bacteria should be able to grow and cycle nutrients more efficiently 18 , 19 . Structural differences between molecules in plastic leachate and natural DOM could similarly enhance bacterial growth by providing more niches for decomposition 20 . Previous studies 8 , 9 , 11 have shown how the response of bacteria to plastic leachate can vary, but, to our knowledge, no study has tested whether the molecular composition of DOM may explain this variation. Recent advances in ultra-high-resolution mass spectrometry now provide an opportunity to address this question 21 , 22 , 23 .

The responses of bacteria to plastic leachate should vary across waters for at least two reasons. First, the molecular composition of natural DOM varies among lakes and rivers 24 , 25 , and so should influence the ability of bacteria to use plastic leachate. In most of the world’s lakes, DOM is dominated by relatively recalcitrant compounds 26 , 27 , limiting opportunities for decomposition 20 , 28 . Plastic leachate that is more labile may therefore be widely assimilated in lakes containing this recalcitrant carbon. By contrast, leachate may have little benefit to bacteria in waters with already highly labile DOM, or it may be used similarly to natural DOM that it resembles chemically, as bacteria will be preadapted to use these substrates 29 . Second, the functional composition of bacterial communities, and thus their ability to utilise natural DOM, varies across space because of different environmental conditions, dispersal histories, and stochastic processes 30 , 31 , 32 , 33 . The same pattern should also be seen for DOM derived from plastic leachate.

Here, our aim was to determine the effects of plastic leachate on bacteria in the northern lakes that dominate the world’s freshwater area 34 . We hypothesised that the molecular composition of pre-existing lake DOM controls how bacteria respond to plastic leachate. To test our hypothesis, we incubated surface waters from 29 lakes of varying DOM composition either with or without leachate from low-density polyethylene (LDPE) plastic bags, the most common plastic in freshwaters 35 . We added either an environmentally representative amount of this leachate (0.1 mg C L −1 ; Supplementary Methods  1 ), which was much less than used in previous studies 8 , 9 , 11 , or an identical volume of a distilled water control to surface lake water. Using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), we compared the molecular composition of DOM in our plastic leachate to that naturally occurring in our study lakes. We also measured bacteria protein production (BPP), which reflects bacterial biomass acquisition 36 , and bacterial growth efficiency (BGE). BGE allows us to separate whether BPP increases with leachate simply because more carbon is available or because the added carbon is also more labile and thus more accessible to bacteria. In the former case, BGE would remain unchanged, as any increase in BPP would purely result from an increase in the absolute amount of carbon processed rather than any change in how it was processed. In the latter case, BGE would increase with BPP because the carbon would be processed more efficiently, such as if it was more bioavailable to resident bacterial communities. We further tested how the responses of BPP and BGE to plastic leachate varied with microbial community structure and which taxa were associated with these responses using 16S amplicon sequencing. Our work now advances previous studies by showing that the effects of plastic leachate on BGE strongly depend on the concentration and functional diversity (FD) of existing lake DOM, thereby explaining variation in the responses reported to date 8 , 9 , 11 .

Plastic leachate is more labile than natural organic matter

DOM from plastic leachate was distinct from that in lakes in three main ways. First, it had less diversity in the potential functions (i.e. reactivity) of molecular formulas. We used a widespread functional diversity (FD) index to calculate the expected mass difference between molecules in the dataset. The FD of plastic leachate was 3.46, lower than any of the 22 lakes in which we measured FD. In these lakes, FD ranged from 6.12 to 6.96, indicating more variation in the potential size range of molecules available for microbial activity. These differences were mirrored by the total number of molecular formulas that we detected in our analytical window (150–2000 Da): 855 in the leachate versus between 3684 to 7116 in natural lake DOM. Second, despite being less diverse, plastic leachate had a much higher lability index. Of the molecular formulas detected in the plastic leachate, 18.6% had a high lability index 21 (i.e. H:C ratio ≥1.5), exceeding proportions found in any of our 22 study lakes, which ranged from 10.3 to 12.5%. Although the lakes did have a greater absolute number of compounds with a high lability index given their larger number of molecular formulas, highly labile compounds were relatively less abundant (5.4–10.6%) in lakes than within plastic leachate where they accounted for 82.2% of the normalised peak intensity. Compared to a freshwater standard widely used in mass spectrometry, the plastic leachate also had a greater H:C ratio, a lower O:C ratio, fewer molecular formulas, and a greater percentage of formulas with a high lability index (Fig.  1 ). Finally, 35% of molecular formulas in the plastic leachate were unique and absent from our 22 study lakes. This value likely underestimated the true difference. Of our study lakes, we previously surveyed 19 for pollution impacts and all were contaminated with microplastics and anthropogenic fibres 37 . Thus, it is likely we detected associated plastic-derived compounds in DOM of these lakes. Our approach also resolved molecular formulas and not structures, so identical formulas between plastic leachate and lake DOM could represent different molecules. Irrespective, 11 of the formulas unique to the leachate corresponded to known chemical additives used in plastic production, such as isophthalic acid and phthalates, and 2 corresponded to known breakdown products unique to plastics (Table  1 ).

We compared molecular formulae retrieved from FT-ICR-MS in ( a ) plastic leachate with ( b ) a freshwater standard sample widely used in mass spectrometry. Dots are individual molecular formula, with density representing the number of identical formulae along axes of H:C and O:C. Molecules were classed as having a high lability index based on a H:C ratio ≥1.5 after D’Andrilli et al. 21 .

Bacteria grow faster and more efficiently when offered a small amount of plastic leachate

Plastic leachate increased both the BPP and BGE of natural bacterial communities after 3 days despite adding little carbon to lake DOM. The addition of plastic leachate increased mean [95% confidence interval, CI] BPP by 2.29 [1.92, 2.73] times compared to the control treatment (Fig.  2 ). Specifically, BPP increased from an estimated mean of 0.078 [0.058, 0.105] μg C L −1 hr −1 under the control treatment to 0.178 [0.132, 0.240] μg C L −1 hr −1 under the plastic treatment. We also found that bacterial growth was more efficient in the presence of plastic leachate than when only natural lake DOM was available. The addition of plastic leachate increased BGE by 1.72 [1.27, 2.32] times compared to the control treatment (Fig.  3a ). Specifically, BGE increased from an estimated mean of 8.1 [5.8, 11.5] % in the control treatment to 14.0 [10.0, 19.5] % in the plastic treatment. To sustain a mean increase in BPP of 7.31 µg C L −1 over the 72 h of our incubation with the estimated BGE of 14.0 [10.0, 19.5] %, bacteria would have to process a mean of 51.5 [37.0, 72.1] µg C L −1 , which is half that added by the leachate.

Bolded line shows the mean increase in BPP between treatment means ± 95% confidence intervals. Thin lines join mean effects for each of the 29 study lakes ( n  = 3 replicates per treatment per lake).

a Bolded line shows mean ± 95% CI for BGE in each treatment. Thin lines join mean effects for each of 18 study lakes with respiration data ( n  = 1 replicate per treatment per lake). BGE increased relatively less with plastic leachate addition as either the ( b ) functional diversity of lake dissolved organic matter (DOM) increased, ( c ) lake dissolved organic carbon (DOC) concentration increased, or ( d ) lake bacterial diversity decreased. Bolded lines are the estimated means ± 95% CIs for the trends and points are observed changes in BGE with plastic leachate addition. Horizontal line indicates no change in BGE with leachate addition (i.e. fold change = 1), whereas values above and below indicate an increase and decrease in BGE, respectively.

Plastic leachate is used most efficiently in lakes with less diverse DOM

Plastic leachate led to relatively greater increases in BGE in lakes with less functionally diverse DOM and less DOM itself (Fig.  3 ). We detected interactions between the plastic treatment and both lake FD and lake dissolved organic carbon (DOC) concentration (Fig.  3b, c ). At a low FD, i.e. 1 standard deviation (SD) beneath the mean, bacteria were more efficient in the presence of plastics: BGE increased by a mean [95% CI] of 2.31 [1.54, 2.31] times from an estimated mean of 2.57 [1.71, 3.86] % to 5.93 [3.95, 8.89] %. In contrast, at a high FD (i.e. 1 SD above the mean), there was no change in BGE when plastic leachate was added: 1.18 [0.50, 2.80] times difference. BGE varied similarly with lake DOC concentration. At a low DOC concentration, BGE increased by 3.43 [2.82, 4.15] times from an estimated mean of 1.69 [1.39, 2.05] % to 5.77 [4.75, 6.99] %, whilst at a high DOC concentration there was no effect of plastic addition with a 0.74 [0.27, 2.04] times difference in BGE. Neither FD nor DOC influenced the extent to which BPP varied with plastic leachate, as the Akaike information criterion (AIC) increased by 1.52 and decreased only by 1.93, respectively, from retaining these treatment interactions during model selection. The absence of these interactions, despite influencing BGE, may ultimately reflect site-specific differences in the metabolic costs for bacteria to exploit available carbon (Supplementary Fig.  3 ). Other environmental variables retained as predictors of BGE during model selection, specifically water temperature, pH, and latitude, also did not influence the response of BGE to plastic leachate (ΔAIC from including interactions with leachate treatment: 0.24, 1.36, and 0.27, respectively).

Bacterial diversity affects the efficiency of plastic leachate usage

The effect of plastic leachate on BGE varied with the diversity of bacteria present in the lake, as expected if microbial community composition influenced the use of novel DOM sources. We retrieved 2148 amplicon sequence variants (ASVs) across 20 lakes subjected to 16S amplicon sequencing. Community composition was dominated by the genera Acinetobacter , Exiguobacterium , and Brevundimonas (Supplementary Fig.  4 ). We then summarised differences in bacterial diversity using the Shannon index, which ranged between 3.46 to 6.38 per lake, similar to other studies in northern waters 38 . We found that bacterial diversity interacted with the plastic treatment to influence BGE (Fig.  3d ). At high bacterial diversity, plastic leachate addition increased BGE 2.93 [1.71, 5.03] times from an estimated mean of 6.59 [3.84, 11.3] % to 19.3 [11.2, 33.1] %. There was no effect of plastic addition at low bacterial diversity with a 1.08 [0.58, 1.99] times difference. Bacterial diversity also had no effect on the response of BPP to leachate addition, as expected if taxa did not strongly discriminate in their use of labile, plastic-derived compounds, but instead used them with varying efficiency (ΔAIC from retaining interaction: 1.66).

To identify which genera responded most strongly to the plastic leachate, we tested if some ASVs were more abundant when BPP and BGE increased after leachate addition. We found that the fold increases in BPP and BGE were positively correlated with 154 and 540 ASVs, respectively (Supplementary Fig.  4 ). BPP and BGE increased most with the fold increase in ASVs that belonged to the genera Hymenobacter and Deinococcus , respectively (Supplementary Fig.  4 ).

Here we found that plastic-derived DOM was substantially different to natural DOM and that it strongly promoted bacterial growth. Plastic leachate more than doubled bacterial biomass production relative to the control treatment despite adding a mean (±SD) of only 4.5 ± 4.0% of the total lake DOC concentrations. As much of the carbon provided by the plastic leachate had to be assimilated to sustain the increase in BPP, given the mean BGE, this result further highlights the bioavailability of plastic leachate for use by microbial communities. Although the increase in BPP was less than the over 4-times increase reported in oceans by Romera-Castillo et al. 8 , we added 7.4-times less DOC to replicate concentrations observed in lakes near population centres (Supplementary Methods  1 ). Therefore, we found strong effects of plastics at environmentally relevant concentrations, although differences between our study and others may be due to differences in the characteristics of background waters. These positive effects may disappear at higher leachate concentrations and/or in different waters, as found by Tetu et al. 11 who added 1.3- to 250-times more plastic-derived DOM than us into artificial seawater. By characterising the unique molecular properties of plastic leachate, our study now adds novel insight into why and when leachate stimulates bacterial growth. Specifically, the high lability and bioavailability of the plastic leachate likely increased BPP and BGE, as occurs with DOC in the natural environment 18 , 19 , 39 , 40 . An additional quantity of carbon from plastic leachate is unlikely to be the sole explanation for these results as it comprised only a small fraction of the total DOC pool. Our results also suggest that high plastic leachate concentrations, such as used by Tetu et al. 11 , may impair bacterial growth because they add large quantities of toxic compounds, e.g. oxybenzone 41 , 42 .

Increases in BGE varied with lake DOM concentration and composition, suggesting that the local environment mattered in addition to the leachate. As BGE, but not BPP, interacted with lake characteristics, local bacterial communities must have produced similar biomass at low and high FD/DOC concentrations but with lower metabolic costs in the former. Lower costs could arise because DOM contained proportionally more molecules with a high lability index at low FD/DOC concentrations once we added leachate to lake water (Supplementary Fig.  3 ). There may be lower metabolic costs when microbes have more labile substrates to consume, such as if it permits them to target molecules that are more thermodynamically available 43 . Microbial communities in these environments could have also specialised towards those that produce more efficient enzymes for degrading the available resources 30 , 44 . FD can reflect the number of niches available for microbial decomposers 20 , 23 . Therefore, bacteria in lakes with few niches (i.e. low FD) may benefit most from the high-lability-index molecules that we found were added by plastic leachate. Taken together, this dependency of bacteria on pre-existing DOM can explain why their responses have varied in studies of plastic leachate that have used different source waters 8 , 11 . More generally, our results suggest that how microbes respond to plastic leachate depends on both the number of potential microbial niches conferred by existing DOM and the capacity of local communities to occupy these niches.

Microbial diversity also influenced the increase in BGE after leachate addition. We specifically found that increases in BGE after leachate addition were amplified at higher levels of bacterial diversity. Greater diversity may increase the likelihood of taxa that can use plastic-derived compounds efficiently, thereby elevating the BGE of the entire community. To our knowledge, no study has explored how bacterial diversity influences the extent to which BGE responds to resource manipulation. Previous studies have instead correlated BGE to bacterial richness 45 , 46 , and changes in BGE to bacterial community composition 47 . More broadly, our results offer promise that some taxa may be particularly well suited to use plastic-derived compounds and remove them from the natural environment.

By providing an understanding of when plastic leachate is used by natural communities, our findings have wider implications for aquatic food webs and pollution mitigation efforts. First, more biomass at the base of the food webs will transfer more energy into higher trophic levels, stimulating the growth of higher organisms 48 , 49 . For example, Daphnia grew as quickly on microplastics as when fed algae 10 , indicating that the increase in bacterial production from plastic-derived carbon can support the growth of higher trophic levels. Second, our results offer insight for efforts to identify environmental isolates that might remove plastic-derived compounds from the natural environment. Specifically, we found ASVs in the genera Deinococcus and Hymenobacter were associated with high levels of plastic leachate use, consistent with previous observations of microbial communities associated with biodegradable plastic films 50 . Deinococcus taxa have also been shown to match DNA sequences encoding a recently identified polyethylene terephthalatase enzyme from Ideonella sakaiensis 51 . Other taxa positively correlated with bacterial metabolism included Exiguobacterium , which were previously found to grown solely on polystyrene film 52 . However, bacteria capable of utilising leachates may differ from those that degrade plastic itself. Recent studies have isolated phylogenetically divergent bacteria with the ability to degrade plastics, including strains of Proteobacteria—such as Pseudomonas spp. 53 , 54 , 55 , Rhodobacteraceae 56 , Ideonella sakaiensis 57 , and Acinetobacter baumannii 58 —and Firmicutes such as Bascillus spp. 53 , 55 . Many of these taxa were strongly associated with BPP and BGE in our study (Supplementary Fig.  4 ). Irrespective of whether the microbes using leachates are the same as those decomposing it, the ability to uptake leachates is important for reducing chemical pollution from plastics 11 , 59 and our results identifying taxa that do so can help direct biological remediation efforts.

Our study has at least three limitations despite identifying clear effects of plastics on the metabolism of microbial communities. First, we focused solely on bacteria, but other microorganisms such as microalgae and fungi are also affected by plastics and plastic leachates 60 , 61 , 62 , 63 . These additional interactions may further influence the overall response of ecosystem metabolism to plastic pollution in addition to the effects of bacteria observed here. Second, we only leached LDPE. The chemical composition of leachate from other plastics will likely differ and so the type of plastic present within lakes may also influence bacteria alongside the local environment. However, LDPE is the most common plastic found in aquatic systems 35 , so should contribute most to the DOM pool available for use by bacteria. Finally, our study used a single LDPE concentration that was representative of plastic concentrations found in lakes near population centres (Supplementary Methods  1 ). Higher concentrations, such as found at waste management sites, may have less positive effects on microorganisms, especially if higher concentrations of toxic additives accumulate 11 . Irrespective, plastics will pollute the environment for decades 64 . Our findings are therefore valuable as they suggest that some lakes (e.g. high DOC concentrations, functionally diverse DOM, low bacterial diversity) are least able to remove leachate dissolved from plastics and so would benefit most from future pollution management.

Lake sampling

We sampled 29 lakes across Scandinavia between August and September 2019. The lakes were located between latitudes of 59.1°N and 70.3°N to capture broad environmental gradients (Supplementary Fig.  1 ). For example, the lakes differed in depth (range: 0.9–303 m) and area (0.01–464 km 2 ), and, at the time of sampling, they differed in mean surface temperature (9.4–20.6 °C), pH (5.81–6.95), DOC concentration (0.55–7.97 mg L −1 ), and DOM functional diversity (6.12–6.96).

Lakes were sampled at their deepest point. We collected 10 L of surface water in an acid washed Nalgene bottle. At 20 lakes, we immediately preserved microbial community composition by passing 1000 mL of water through a 0.2 µm Sterivex filter unit (Millipore). Filters were stored at −20 °C until laboratory analyses. We then measured the pH and temperature of lake water using a multiprobe (HI-99171, Hanna Instruments). Finally, total nitrogen (TN), DOC and DOM were sampled at 22 lakes by filtering 500 mL of water through pre-combusted glass fibre filters (0.5 µm nominal pore size, Macherey-Nagel) into three glass amber bottles with no headspace. Bottles were acidified to pH 2 with 0.5 mL of 10% HCl and stored in the dark. Remaining water was stored in the Nalgene sampling bottle for up to three hours in the dark before beginning the experiment.

Plastic leachate preparation

Plastic bags made of LDPE—the most common plastic type in freshwaters 35 —were collected from four major shopping chains (John Lewis, Superdrug, Clintons, and Next) in Cambridge, England and cut into 1 cm 2 squares. 240 squares (60 from each shopping chain) were incubated in 150 mL of distilled water at 25 °C for 7 days under an LED lamp that simulated natural UV exposure (395–530 nm wavelength, 100 µmol photons m −2 s −1 light intensity) and with constant agitation to simulate environmental transport 8 . A separate flask of 125 mL of distilled water without the plastics was also incubated under the same conditions as a control that confirmed no DOM was leached from our treatment process. At the end of the incubation, water was filtered for use in the experiment through pre-rinsed 0.2 µm cellulose acetate syringe filters (Sartorius AG) into dark, pre-combusted glass vials with no headspace. We used a more restrictive filter size than when preserving lake DOM as we wanted to ensure absolutely no lab microbes could contaminate the experimental treatments and be introduced into lake waters. The incubations were preserved for DOM and DOC measurements as for lake waters. We used water from the 0.2 µm filtrate rather than a higher pore size like in the lakes to measure precisely what was added in the experimental treatments.

DOM characterisation

We estimated the functional diversity (FD) of lake water and plastic leachate DOM using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The DOM was solid phase extracted as previously described in Dittmar et al. 22 . Briefly, the DOM from the 500 mL bottles was retained on 1 g of a styrene-divinylbenzene polymer (Bond Elut PPL, Agilent) and eluted with 4 mL of ultrapure methanol (LC-MS LiChrosolv, Merk). The resulting extracts were diluted in a 1:1 (v:v) methanol:water solution to a final concentration of 2.5 ppm. 100 µL of the diluted extracts were directly infused in negative mode via electrospray ionisation into a 15 Tesla Solarix XR FT-ICR-MS (Bruker Daltonics, Germany). 200 scans were collected for each lake, and the scans were then calibrated using DataAnalysis software (Bruker Daltonics, Germany). Masses in the range 150 to 1000 m/z were exported and the online platform ICBM-OCEAN 65 used to assign molecular formulas. FD was computed as in Mentges et al. 23 , using differences in the number of carbon atoms in the molecular formulas, whereby a greater value indicated more diversity in the size of the molecular formulas. We also estimated the bioavailability of the plastic leachate and the lake water DOM by classifying molecular formulas with a H:C ratio ≥1.5 as having a high lability index 21 . DOC and TN concentrations in the samples were measured within a month of sampling on a Shimadzu TOC-L TNM-L analyser (Shimadzu Corporation, Japan).

Experimental design

At each lake, incubations were set up to test the effect of plastic leachate (Supplementary Fig.  2 ). Nine 125 mL glass bottles were filled with 125 mL of the collected lake water. Three bottles received either 4.6 mL of leachate, 4.6 mL of distilled water, or no further addition. The volume of leachate was determined so that 0.1 mg C L −1 was added. This concentration was assumed to be representative of the amount of carbon leached from plastics in the environment based on: (1) the concentration of plastics in lakes near cities in southern Europe, (2) the density and volume of LDPE plastic bags, and (3) the expected leaching rate of plastics (calculations in Supplementary Methods  1 ). Bottles were crimped airtight with PTFE/rubber septa, ensuring that there were no bubbles present before proceeding. Pure lake water bottles were processed directly to provide measurements for the start of the incubation, whilst bottles that received the distilled water or plastic leachate addition were incubated for 72 h in the dark at ambient temperature. Identical vials were also prepared for oxygen concentration measurements to derive BGE. Lake water with either plastic leachate or lake water with distilled water—as previously described—were added to gastight 25 mL glass vials in triplicate with no headspace. Plastic leachate or distilled water (0.9 mL) was added to the same concentration (0.1 mg C L −1 ) as the incubation described above.

Bacterial activity

To determine bacterial activity, BPP and respiration were measured after a 72-h incubation. Bacterial productivity was estimated based on protein production using carbon uptake as a proxy 36 . Briefly, 17 nM of [ 3 H]-leucine was added to 1.5 mL of sample water collected from each incubation bottle into a 2 mL centrifuge tube. 300 µL of 50% trichloroacetic acid (TCA) was then added to one sample from each treatment in each lake (hereafter referred to as “killed”) with nothing added to the other sample (hereafter referred to as “live”). All samples were incubated in the dark at lake temperature for 1 h. At the end of the incubation, 300 µL of 50% TCA was added to the live samples. Cells were precipitated by centrifugation (10 min, 16,000 ×  g ). Pellets were washed with 1 mL of 5% TCA, centrifuged again (10 min, 16,000 ×  g ), and the supernatant removed. Samples were air dried before adding 1 mL of Optiphase HiSafe 3 liquid scintillation cocktail. Counts per minutes (CPM) were measured using a Triathler liquid scintillation counter (Hidex Oy, Finland), alongside a standard of known concentration and two blanks (1 mL of scintillation fluid only, and an empty Eppendorf tube) used for calibration. CPMs were converted to disintegrations per minute, subtracting the killed and blank from each live value, and adjusting for counting efficiency based on the standard. These values were then converted to carbon uptake 66 .

Oxygen levels in the water were measured before and after the incubation to determine respiration rate. One vial from each treatment was measured immediately, and the other two were measured after 72 h in the dark. We used fibre-optics optodes connected to a OXY-1 ST metre (PreSens, Germany) to record oxygen concentration as percentage of air saturation in each 25 mL vial 67 , 68 . Readings were registered every second until a steady state had been reached—for 90% of samples this was reached within 5 min. Oxygen concentration was then derived from the median of the last 10 stable values in the time series. Pressure, temperature, and salinity were also recorded and used to correct the values to standard conditions.

To determine whether bacteria used carbon efficiently for growth, bacterial growth efficiency (BGE) was calculated as reviewed by del Giorgio and Cole 69 . BPP and respiration were converted to units of moles of carbon per hour, assuming a respiratory quotient of one, and we then calculated the proportion of total carbon incorporated into biomass by dividing the carbon used for growth (BPP) by the sum of BPP and respiration.

Bacterial community composition

In addition to DOM characteristics, we considered how the composition and diversity of bacteria influenced their responses to plastic leachate. To characterise bacterial communities, DNA was extracted from the Sterivex filters following an established protocol 70 with minor modifications.

Briefly, we placed the filters, which were separated from the filtration unit under sterile conditions, into a cryotube containing silica and zirconia beads (3.0, 0.7, and 0.1 mm diameter) before vortexing at 2850 rpm for 15 min. Then, we added 0.6 mL of phenol-chloroform-isopropanol (25:24:1), 0.6 mL of 5% cetrimonium bromide, 60 µl of 10% sodium dodecyl sulfate, and 60 µl 10% N-lauroylsarcosine and vortexed the solution at 2850 rpm for 15 min. We then centrifuged the samples at 16 ×  g for 15 min at 4 °C and collected the supernatant. To the supernatant, we added an equal volume (ca. 0.6 mL) of chloroform-isopropanol (24:1), mixed the samples by inversion, and centrifuged at 16 ×  g for 10 min at 4 °C. We again collected the supernatant and precipitated the DNA at 4 °C overnight in polyethylene glycol with 1.6 M sodium chlorine. We centrifuged the samples again at 17 ×  g for 90 min at 4 °C, removed the supernatant, and washed the pellet with ice-cold (−20 °C) 70% ethanol. The DNA was dissolved in ultrapure water and quantified on a Qubit fluorometer (ThermoFisher, USA). We also extracted DNA from a ZymoBIOMICS™ Microbial Community Standard (Zymo Research, USA) and nuclease-free water (Qiagen, Germany) to act as positive and negative controls, respectively. Libraries were prepared exactly like the lake samples.

We amplified the V6 and V8 regions of the 16S rRNA gene using the bacteria specific primers 71 5’ ACGCGHNRAACCTTACC 3’ and 5’ ACGGGCRGTGWGTRCAA 3’. Samples were sequenced at 2 × 300 bp paired-end on an Illumina MiSeq at the Integrated Microbiome Resource (Halifax, Nova Scotia, Canada) 71 . No DNA was retrieved from the negative control and no contaminants were present in the positive control. We then removed the primers from the raw sequences using cutadapt 72 and assigned taxonomy with the DADA2 pipeline 73 and the Silva v132 database 74 . Overall, 1.7 million reads were classified into 2148 amplicon sequence variants (ASVs), which represented 75% of the total raw reads, and we used these to compute the Shannon diversity index 75 . The raw sequences have been deposited in the EBI database under accession number PRJEB49321 .

Statistical analysis

The effect of plastics on BPP and BGE were tested using linear mixed effects models. As both BPP and BGE were not normally distributed, they were natural log transformed before analysis. We then considered the following fixed predictors for each bacterial response: functional diversity of lake DOM, bacterial diversity (Shannon index), DOC and TN concentrations, lake water temperature, pH, and latitude. The latter variable was included to control for differences in lake location, which is known to influence bacterial community composition 76 , and so which we hypothesised may affect the overall bacterial response. We included an interaction in our model between each predictor and the experimental treatment (i.e. plastic or control treatment), which was also included as a main effect. We accounted for repeated measurements of the same lake by including lake ID as a random effect. Models were initially fitted using maximum-likelihood with the lmer function from the lme4 package in R version 3.5.3 77 . To avoid multicollinearity, we inspected correlations among model parameter estimates. When two variables were correlated with a Pearson correlation r  > 0.90, the most biologically relevant term was selected for inclusion into the model. The best supported model was then determined using backwards stepwise elimination using the drop1 function from lme4 . Fixed effects were dropped if their retention would not have decreased the model’s Akaike information criterion score by more than two. Only results from the best supported model, re-fitted using restricted maximum likelihood, were reported in the main text. Confidence intervals were calculated from these models using the emmeans package 78 .

We identified which ASVs were associated with changes in BPP and BGE after plastic leachate addition. We separately estimated the log2-fold change in the relative abundance of each ASV relative to fold-increases in BGE or BPP by fitting separate negative binomial generalised linear models to read counts using the DESeq function in the DESeq2 79 R package. All ASVs with <100 reads were removed to avoid inferring correlations with rare taxa that may be subject to more stochastic variation in abundance. P values were adjusted to correct for multiple comparisons with the Benjamini–Hochberg method 79 and considered statistically significant beneath a threshold of 0.05.

Reporting summary

Further information on research design is available in the  Nature Research Reporting Summary linked to this article.

Data availability

The BPP and BGE data generated in this study can be downloaded from FigShare ( https://figshare.com/articles/dataset/BPP_data/19692031 ; https://figshare.com/articles/dataset/BGE_data/19692028 ). The DNA sequences can be downloaded from the EBI database ( https://www.ebi.ac.uk/services/dna-rna ) under accession number PRJEB49321 .

da Costa, J. P., Santos, P. S. M., Duarte, A. C. & Rocha-Santos, T. (Nano)plastics in the environment—sources, fates and effects. Sci. Total Environ. 566–567 , 15–26 (2016).

Article   PubMed   CAS   Google Scholar  

Huang, W. et al. Microplastics and associated contaminants in the aquatic environment: a review on their ecotoxicological effects, trophic transfer, and potential impacts to human health. J. Hazard. Mater. 405 , 124187 (2021).

Article   CAS   PubMed   Google Scholar  

Peng, L. et al. Micro- and nano-plastics in marine environment: source, distribution and threats—a review. Sci. Total Environ. 698 , 134254 (2020).

Article   ADS   CAS   PubMed   Google Scholar  

Amaral-Zettler, L. A., Zettler, E. R. & Mincer, T. J. Ecology of the plastisphere. Nat. Rev. Microbiol. 18 , 139–151 (2020).

Galgani, L., Engel, A., Rossi, C., Donati, A. & Loiselle, S. A. Polystyrene microplastics increase microbial release of marine chromophoric dissolved organic matter in microcosm experiments. Sci. Rep. 8 , 14635 (2018).

Article   ADS   PubMed   PubMed Central   CAS   Google Scholar  

Gewert, B., Plassmann, M., Sandblom, O. & MacLeod, M. Identification of chain scission products released to water by plastic exposed to ultraviolet light. Environ. Sci. Technol. Lett. 5 , 272–276 (2018).

Article   CAS   Google Scholar  

Suhrhoff, T. J. & Scholz-Böttcher, B. M. Qualitative impact of salinity, UV radiation and turbulence on leaching of organic plastic additives from four common plastics—A lab experiment. Mar. Pollut. Bull. 102 , 84–94 (2016).

Romera-Castillo, C., Pinto, M., Langer, T. M., Álvarez-Salgado, X. A. & Herndl, G. J. Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean. Nat. Commun. 9 , 1430 (2018).

Zhu, L., Zhao, S., Bittar, T. B., Stubbins, A. & Li, D. Photochemical dissolution of buoyant microplastics to dissolved organic carbon: rates and microbial impacts. J. Hazard. Mater. 383 , 121065 (2020).

Taipale, S. J. et al. Tracing the fate of microplastic carbon in the aquatic food web by compound-specific isotope analysis. Sci. Rep. 9 , 19894 (2019).

Article   ADS   CAS   PubMed   PubMed Central   Google Scholar  

Tetu, S. G. et al. Plastic leachates impair growth and oxygen production in Prochlorococcus , the ocean’s most abundant photosynthetic bacteria. Commun. Biol. 2 , 184 (2019).

Article   PubMed   PubMed Central   Google Scholar  

Ohtake, Y., Kobayashi, T., Asabeb, H. & Murakami’, N. Studies on biodegradation of LDPE—observation of LDPE films scattered in agricultural fields or in garden soil. Polym. Degrad. Stab. 60 , 79–84 (1996).

Article   Google Scholar  

Dekiff, J. H., Remy, D., Klasmeier, J. & Fries, E. Occurrence and spatial distribution of microplastics in sediments from Norderney. Environ. Pollut. 186 , 248–256 (2014).

Hahladakis, J. N., Velis, C. A., Weber, R., Iacovidou, E. & Purnell, P. An overview of chemical additives present in plastics: migration, release, fate and environmental impact during their use, disposal and recycling. J. Hazard. Mater. 344 , 179–199 (2018).

Hansen, E., Nillson, N., Lithner, D. & Lassen, C. Hazardous substances in plastic materials (Klima- og forurensningsdirektoratet, 2013).

Andrady, A. L. The plastic in microplastics: a review. Mar. Pollut. Bull. 119 , 12–22 (2017).

Bond, T., Ferrandiz-Mas, V., Felipe-Sotelo, M. & Sebille, E. V. The occurrence and degradation of aquatic plastic litter based on polymer physicochemical properties: a review. Crit. Rev. Environ. Sci. Technol. 48 , 685–722 (2018).

Middelboe, M. & Søndergaard, M. Bacterioplankton growth yield: seasonal variations and coupling to substrate lability and beta-glucosidase activity. Appl. Environ. Microbiol. 59 , 3916–3921 (1993).

Sobczak, W. V. Epilithic bacterial responses to variations in algal biomass and labile dissolved organic carbon during biofilm colonization. J. North Am. Benthol. Soc. 15 , 143–154 (1996).

Tanentzap, A. J. et al. Chemical and microbial diversity covary in fresh water to influence ecosystem functioning. PNAS 116 , 24689–24695 (2019).

D’Andrilli, J., Cooper, W. T., Foreman, C. M. & Marshall, A. G. An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability. Rapid Commun. Mass Spectrom. 29 , 2385–2401 (2015).

Dittmar, T., Koch, B., Hertkorn, N. & Kattner, G. A simple and efficient method for the solid-phase extraction of dissolved organic matter (SPE-DOM) from seawater. Limnol. Oceanogr. Methods 6 , 230–235 (2008).

Mentges, A., Feenders, C., Seibt, M., Blasius, B. & Dittmar, T. Functional molecular diversity of marine dissolved organic matter is reduced during degradation. Front. Mar. Sci. 4 , 194 (2017).

Kellerman, A. M., Dittmar, T., Kothawala, D. N. & Tranvik, L. J. Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology. Nat. Commun. 5 , 3804 (2014).

Wagner, S. et al. Linking the molecular signature of heteroatomic dissolved organic matter to watershed characteristics in world rivers. Environ. Sci. Technol. 49 , 13798–13806 (2015).

Massicotte, P., Asmala, E., Stedmon, C. & Markager, S. Global distribution of dissolved organic matter along the aquatic continuum: across rivers, lakes and oceans. Sci. Total Environ. 609 , 180–191 (2017).

Rasmussen, J. B., Godbout, L. & Schallenberg, M. The humic content of lake water and its relationship to watershed and lake morphometry. Limnol. Oceanogr. 34 , 1336–1343 (1989).

Article   ADS   CAS   Google Scholar  

Mostovaya, A., Hawkes, J. A., Dittmar, T. & Tranvik, L. J. Molecular determinants of dissolved organic matter reactivity in lake water. Front. Earth Sci. 5 , 106 (2017).

Megharaj, M., Wittich, R.-M., Blasco, R., Pieper, D. H. & Timmis, K. N. Superior survival and degradation of dibenzo-p-dioxin and dibenzofuran in soil by soil-adapted Sphingomonas sp. strain RW1. Appl. Microbiol. Biotechnol. 48 , 109–114 (1997).

Fitch, A., Orland, C., Willer, D., Emilson, E. J. S. & Tanentzap, A. J. Feasting on terrestrial organic matter: dining in a dark lake changes microbial decomposition. Glob. Change Biol. 24 , 5110–5122 (2018).

Article   ADS   Google Scholar  

Orland, C. et al. Microbiome functioning depends on individual and interactive effects of the environment and community structure. ISME J. 13 , 1–11 (2019).

Ruiz‐González, C., Niño‐García, J. P., Lapierre, J.-F. & Giorgio, P. A. D. The quality of organic matter shapes the functional biogeography of bacterioplankton across boreal freshwater ecosystems. Glob. Ecol. Biogeogr. 24 , 1487–1498 (2015).

Wilhelm, L. et al. Altitudinal patterns of diversity and functional traits of metabolically active microorganisms in stream biofilms. ISME J. 9 , 2454–2464 (2015).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Verpoorter, C., Kutser, T., Seekell, D. A. & Tranvik, L. J. A global inventory of lakes based on high-resolution satellite imagery. Geophys. Res. Lett. 41 , 6396–6402 (2014).

Andrady, A. L. Microplastics in the marine environment. Mar. Pollut. Bull. 62 , 1596–1605 (2011).

Simon, M. & Azam, F. Protein content and protein synthesis rates of planktonic marine bacteria. Mar. Ecol. Prog. Ser. 51 , 201–213 (1989).

Tanentzap, A. J. et al. Microplastics and anthropogenic fibre concentrations in lakes reflect surrounding land use. PLOS Biol. 19 , e3001389 (2021).

Kraemer, S. A. et al. A large-scale assessment of lakes reveals a pervasive signal of land use on bacterial communities. ISME J. 14 , 3011–3023 (2020).

Apple, J. K. & del Giorgio, P. A. Organic substrate quality as the link between bacterioplankton carbon demand and growth efficiency in a temperate salt-marsh estuary. ISME J. 1 , 729–742 (2007).

del Giorgio, P. A. & Newell, R. E. I. Phosphorus and DOC availability influence the partitioning between bacterioplankton production and respiration in tidal marsh ecosystems. Environ. Microbiol. 14 , 1296–1307 (2012).

Lozano, C. et al. Toxicity of UV filters on marine bacteria: combined effects with damaging solar radiation. Sci. Total Environ. 722 , 137803 (2020).

Mao, F., He, Y., Kushmaro, A. & Gin, K. Y.-H. Effects of benzophenone-3 on the green alga Chlamydomonas reinhardtii and the cyanobacterium Microcystis aeruginosa . Aquat. Toxicol. 193 , 1–8 (2017).

Boye, K. et al. Thermodynamically controlled preservation of organic carbon in floodplains. Nat. Geosci. 10 , 415–419 (2017).

Baña, Z., Ayo, B., Marrasé, C., Gasol, J. M. & Iriberri, J. Changes in bacterial metabolism as a response to dissolved organic matter modification during protozoan grazing in coastal Cantabrian and Mediterranean waters. Environ. Microbiol. 16 , 498–511 (2014).

Reinthaler, T., Winter, C. & Herndl, G. J. Relationship between bacterioplankton richness, respiration, and production in the southern North Sea. Appl. Environ. Microbiol . 71 , 2260–2266 (2005).

Xu, J. et al. Effect of seawater–sewage cross-transplants on bacterial metabolism and diversity. Microb. Ecol. 66 , 60–72 (2013).

Article   PubMed   Google Scholar  

Attermeyer, K. et al. Effects of light and autochthonous carbon additions on microbial turnover of allochthonous organic carbon and community composition. Microb. Ecol. 69 , 361–371 (2015).

Robbins, C. J. et al. Low-level dissolved organic carbon subsidies drive a trophic upsurge in a boreal stream. Freshw. Biol. 65 , 920–934 (2020).

Tanentzap, A. J. et al. Forests fuel fish growth in freshwater deltas. Nat. Commun. 5 , 4077 (2014).

Bandopadhyay, S. et al. Soil microbial communities associated with biodegradable plastic mulch films. Front. Microbiol. 11 , 587074 (2020).

Gambarini, V. et al. Phylogenetic distribution of plastic-degrading microorganisms. mSystems 6 , e01112–e01120.

Yang, Y. et al. Biodegradation and mineralization of polystyrene by plastic-eating mealworms: part 2. Role of gut microorganisms. Environ. Sci. Technol. 49 , 12087–12093 (2015).

León-Zayas, R., Roberts, C., Vague, M. & Mellies, J. L. Draft genome sequences of five environmental bacterial isolates that degrade polyethylene terephthalate plastic. Microbiol. Resour. Announc. 8 , e00237–19 (2019).

Taghavi, N., Singhal, N., Zhuang, W.-Q. & Baroutian, S. Degradation of plastic waste using stimulated and naturally occurring microbial strains. Chemosphere 263 , 127975 (2021).

Roberts, C., Edwards, S., Vague, M., León-Zayas, R., Scheffer, H., Chan, G., Swartz, N. A. & Mellies, J. L. Environmental consortium containing Pseudomonas and Bacillus species synergistically degrades polyethylene terephthalate plastic. mSphere 5 , e01151-20 (2020).

Meyer-Cifuentes, I. E. et al. Synergistic biodegradation of aromatic-aliphatic copolyester plastic by a marine microbial consortium. Nat. Commun. 11 , 5790 (2020).

Yoshida, S. et al. A bacterium that degrades and assimilates poly(ethylene terephthalate). Science 351 , 1196–1199 (2016).

Hussein, A. A., Alzuhairi, M. & Aljanabi, N. H. Degradation and depolymerization of plastic waste by local bacterial isolates and bubble column reactor. AIP Conf. Proc. 1968 , 030081 (2018).

Groh, K. J. et al. Overview of known plastic packaging-associated chemicals and their hazards. Sci. Total Environ. 651 , 3253–3268 (2019).

Prata, J. C., da Costa, J. P., Lopes, I., Duarte, A. C. & Rocha-Santos, T. Effects of microplastics on microalgae populations: a critical review. Sci. Total Environ. 665 , 400–405 (2019).

Schiavo, S., Oliviero, M., Chiavarini, S., Dumontet, S. & Manzo, S. Polyethylene, polystyrene, and polypropylene leachate impact upon marine microalgae Dunaliella tertiolecta . J. Toxicol. Environ. Health Part A 84 , 249–260 (2021).

Luo, H. et al. Leaching behavior of fluorescent additives from microplastics and the toxicity of leachate to Chlorella vulgaris . Sci. Total Environ. 678 , 1–9 (2019).

Kettner, M. T., Rojas‐Jimenez, K., Oberbeckmann, S., Labrenz, M. & Grossart, H. Microplastics alter composition of fungal communities in aquatic ecosystems. Environ. Microbiol. 19 , 4447–4459 (2017).

Borrelle, S. B. et al. Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution. Science 369 , 1515–1518 (2020).

Merder, J. et al. ICBM-OCEAN: processing ultrahigh-resolution mass spectrometry data of complex molecular mixtures. Anal. Chem . 92 , 6832–6838 (2020).

Bade, D., Houser, J. & Scanger, S. Methods of the cascading trophic interactions project (Center for Limnology, University of Wisconsin–Madison, 1998).

Attermeyer, K., Premke, K., Hornick, T., Hilt, S. & Grossart, H.-P. Ecosystem-level studies of terrestrial carbon reveal contrasting bacterial metabolism in different aquatic habitats. Ecology 94 , 2754–2766 (2013).

Klimant, I., Meyer, V. & Kühl, M. Fiber-optic oxygen microsensors, a new tool in aquatic biology. Limnol. Oceanogr. 40 , 1159–1165 (1995).

del Giorgio, P. A. & Cole, J. J. Bacterial growth efficiency in natural aquatic systems. Annu. Rev. Ecol. Evol. Syst. 29 , 503–541 (1998).

Nercessian, O., Noyes, E., Kalyuzhnaya, M. G., Lidstrom, M. E. & Chistoserdova, L. Bacterial populations active in metabolism of C1 compounds in the sediment of Lake Washington, a freshwater lake. Appl. Environ. Microbiol. 71 , 6885–6899 (2005).

Comeau, A. M., Douglas, G. M. & Langille, M. G. I. Microbiome helper: a custom and streamlined workflow for microbiome research. mSystems 2 , e00127–16 (2017).

Martin, M. Cutadapt removes adapter sequences from high-throughput sequencing reads. EMBnet J. 17 , 10–12 (2011).

Callahan, B. J. et al. DADA2: High-resolution sample inference from Illumina amplicon data. Nat. Methods 13 , 581–583 (2016).

Quast, C. et al. The SILVA ribosomal RNA gene database project: improved data processing and web-based tools. Nucleic Acids Res. 41 , D590–D596 (2013).

Shannon, C. E. A mathematical theory of communication. Bell Syst. Tech. J. 27 , 379–423 (1948).

Article   MathSciNet   MATH   Google Scholar  

Fuhrman, J. A. et al. A latitudinal diversity gradient in planktonic marine bacteria. PNAS 105 , 7774–7778 (2008).

Bates, D., Maechler, M., Bolker, B. & Walker, S. Fitting linear mixed-effects models using lme4. J. Stat. Softw. 67 , 1–48 (2015).

Lenth, R. V. emmeans: estimated marginal means, aka least-squares means , https://CRAN.R-project.org/package=emmeans (2021).

Love, M. I., Huber, W. & Anders, S. Moderated estimation of fold change and dispersion for RNA-seq data with DESeq2. Genome Biol. 15 , 550 (2014).

Article   PubMed   PubMed Central   CAS   Google Scholar  

Download references

Acknowledgements

We thank Carolyn Ewins, Sophie Guillaume, and Sam Woodman for help with field work. This work was funded by a H2020 ERC Starting Grant 804673 to AJT.

Author information

Authors and affiliations.

Ecosystems and Global Change Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom

Eleanor A. Sheridan, Jérémy A. Fonvielle, Samuel Cottingham, Yi Zhang & Andrew J. Tanentzap

Department of Zoology, University of Cambridge, The David Attenborough Building, Cambridge, CB2 3QZ, United Kingdom

Eleanor A. Sheridan & David C. Aldridge

Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, 26129, Oldenburg, Germany

Thorsten Dittmar

Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg (HIFMB), 26129, Oldenburg, Germany

You can also search for this author in PubMed   Google Scholar

Contributions

E.A.S., J.A.F., D.C.A, and A.J.T. designed the study. E.A.S., J.A.F., S.C., and Y.Z. performed experimental work. E.A.S., J.A.F., T.D., and A.J.T. analysed data. T.D., D.C.A., and A.J.T. supervised the study. E.A.S., J.A.F., and A.J.T. wrote the first draft of the manuscript and all co-authors commented on and approved the final manuscript.

Corresponding authors

Correspondence to Eleanor A. Sheridan or Andrew J. Tanentzap .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Peer review

Peer review information.

Nature Communications thanks Isaac Dennis Amoah, Sara Rodríguez-Mozaz and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.  Peer reviewer reports are available.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary information, peer review file, reporting summary, rights and permissions.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Sheridan, E.A., Fonvielle, J.A., Cottingham, S. et al. Plastic pollution fosters more microbial growth in lakes than natural organic matter. Nat Commun 13 , 4175 (2022). https://doi.org/10.1038/s41467-022-31691-9

Download citation

Received : 10 June 2021

Accepted : 29 June 2022

Published : 26 July 2022

DOI : https://doi.org/10.1038/s41467-022-31691-9

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

Plastiphily is linked to generic virulence traits of important human pathogenic fungi.

• Gerasimos Gkoutselis
• Stephan Rohrbach
• Gerhard Rambold

Communications Earth & Environment (2024)

Plastics in the environment in the context of UV radiation, climate change and the Montreal Protocol: UNEP Environmental Effects Assessment Panel, Update 2023

• Marcel A. K. Jansen
• Anthony L. Andrady

Photochemical & Photobiological Sciences (2024)

A genome catalogue of lake bacterial diversity and its drivers at continental scale

• Rebecca E. Garner
• Susanne A. Kraemer
• David A. Walsh

Nature Microbiology (2023)

Chemodiversity of soil dissolved organic matter affected by contrasting microplastics from different types of polymers

• Wenbing Tan

Frontiers of Environmental Science & Engineering (2023)

Consequences of Microplastics on Global Ecosystem Structure and Function

• Junhong Bai
• Matthias C. Rillig

Reviews of Environmental Contamination and Toxicology (2023)

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

The World's Plastic Pollution Crisis Explained

Much of the planet is swimming in discarded plastic, which is harming animal and possibly human health. Can it be cleaned up?

Conservation

Children Play among Plastic

While plastic pollution is a worldwide problem it is most obvious in less-wealthy African and Asian nations, like the Philippines. Here, children play among plastic waste on the shore of Manila Bay.

Photograph by Randy Olson

Plastic pollution has become one of the most pressing environmental issues, as rapidly increasing production of disposable plastic products overwhelms the world’s ability to deal with them. Plastic pollution is most visible in less-wealthy Asian and African nations, where garbage collection systems are often inefficient or nonexistent. But wealthy nations, especially those with low recycling rates, also have trouble properly collecting discarded plastics. Plastic trash has become so ubiquitous it has prompted efforts to write a global treaty negotiated by the United Nations. How Did this Happen? Plastics made from fossil fuels are just over a century old. Production and development of thousands of new plastic products accelerated after World War II to the extent that life without plastics would be unimaginable today. Plastics revolutionized medicine with life-saving devices, made space travel possible, lightened cars and jets—saving fuel and lessening pollution —and saved lives with helmets, incubators , and equipment for clean drinking water. The conveniences plastics offer, however, led to a throw-away culture that reveals the material’s dark side: Today, single-use plastics account for 40 percent of the plastic produced every year. Many of these products, such as plastic bags and food wrappers, are used for mere minutes to hours, yet they may persist in the environment for hundreds of years. Plastics by the Numbers Some key facts:

• Half of all plastics ever manufactured have been made in the last 15 years.
• Production increased exponentially, from 2.3 million tons in 1950 to 448 million tons by 2015. Production is expected to double by 2050.
• Every year, about 8 million tons of plastic waste escapes into the oceans from coastal nations. That’s the equivalent of setting five garbage bags full of trash on every foot of coastline around the world.
• Plastics often contain additives making them stronger, more flexible, and durable. But many of these additives can extend the life of products if they become litter, with some estimates ranging to at least 400 years to break down.

How Plastics Move around the World Most of the plastic trash in the oceans, Earth’s last sink, flows from land. Trash is also carried to sea by major rivers, which act as conveyor belts, picking up more and more trash as they move downstream . Once at sea, much of the plastic trash remains in coastal waters. But once caught up in ocean currents, it can be transported around the world. On Henderson Island, an uninhabited atoll in the Pitcairn Group isolated halfway between Chile and New Zealand, scientists found plastic items from Russia, the United States, Europe, South America, Japan, and China. They were carried to the South Pacific by the South Pacific gyre , a circular ocean current. Microplastics Once at sea, sunlight, wind, and wave action break down plastic waste into small particles, often less than half a centimer (one-fifth of an inch) across. These so-called microplastics are spread throughout the water column and have been found in every corner of the globe, from Mount Everest, the highest peak, to the Mariana Trench, the deepest trough . Microplastics are breaking down further into smaller and smaller pieces. Plastic microfibers (or the even smaller nanofibers), meanwhile, have been found in municipal drinking water systems and drifting through the air. Harm to Wildlife Millions of animals are killed by plastics every year, from birds to fish to other marine organisms. Nearly 700 species, including endangered ones, are known to have been affected by plastics. Nearly every species of seabird eats plastics. Most of the deaths to animals are caused by entanglement or starvation. Seals, whales, turtles, and other animals are strangled by  abandoned fishing gear or discarded six-pack rings. Microplastics have been found in more than 100 aquatic species, including fish, shrimp, and mussels destined for our dinner plates. In many cases, these tiny bits pass through the digestive system and are expelled without consequence. But plastics have also been found to have blocked digestive tracts or pierced organs, causing death. Stomachs so packed with plastics reduce the urge to eat, causing starvation. Plastics have been consumed by land-based animals, including elephants, hyenas, zebras, tigers, camels, cattle, and other large mammals, in some cases causing death. Tests have also confirmed liver and cell damage and disruptions to  reproductive systems , prompting some species, such as oysters, to produce fewer eggs. New research shows that larval fish are eating nanofibers in the first days of life, raising new questions about the effects of plastics on fish populations. Stemming the Plastic Tide Once in the ocean, it is difficult—if not impossible—to retrieve plastic waste. Mechanical systems, such as Mr. Trash Wheel, a litter interceptor in Maryland’s Baltimore Harbor, can be effective at picking up large pieces of plastic, such as foam cups and food containers, from inland waters. But once plastics break down into microplastics and drift throughout the water column in the open ocean, they are virtually impossible to recover. The solution is to prevent plastic waste from entering rivers and seas in the first place, many scientists and conservationists—including the National Geographic Society—say. This could be accomplished with improved waste management systems and recycling, better product design that takes into account the short life of disposable packaging, and reduction in manufacturing of unnecessary single-use plastics.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Production Managers

Program specialists, last updated.

October 19, 2023

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Environ Microbiome

Plastics and the microbiome: impacts and solutions

1 School of Biological Sciences, University of Auckland, 3a Symonds Street, Auckland, 1010 New Zealand

J. M. Kingsbury

2 Institute of Environmental Science and Research, 27 Creyke Rd, Ilam, Christchurch, 8041 New Zealand

S. Franchini

V. gambarini, s. d. m. maday, j. a. wallbank.

Global plastic production has increased exponentially since manufacturing commenced in the 1950’s, including polymer types infused with diverse additives and fillers. While the negative impacts of plastics are widely reported, particularly on marine vertebrates, impacts on microbial life remain poorly understood. Plastics impact microbiomes directly, exerting toxic effects, providing supplemental carbon sources and acting as rafts for microbial colonisation and dispersal. Indirect consequences include increased environmental shading, altered compositions of host communities and disruption of host organism or community health, hormone balances and immune responses. The isolation and application of plastic-degrading microbes are of substantial interest yet little evidence supports the microbial biodegradation of most high molecular weight synthetic polymers. Over 400 microbial species have been presumptively identified as capable of plastic degradation, but evidence for the degradation of highly prevalent polymers including polypropylene, nylon, polystyrene and polyvinyl chloride must be treated with caution; most studies fail to differentiate losses caused by the leaching or degradation of polymer monomers, additives or fillers. Even where polymer degradation is demonstrated, such as for polyethylene terephthalate, the ability of microorganisms to degrade more highly crystalline forms of the polymer used in commercial plastics appears limited. Microbiomes frequently work in conjunction with abiotic factors such as heat and light to impact the structural integrity of polymers and accessibility to enzymatic attack. Consequently, there remains much scope for extremophile microbiomes to be explored as a source of plastic-degrading enzymes and microorganisms. We propose a best-practice workflow for isolating and reporting plastic-degrading taxa from diverse environmental microbiomes, which should include multiple lines of evidence supporting changes in polymer structure, mass loss, and detection of presumed degradation products, along with confirmation of microbial strains and enzymes (and their associated genes) responsible for high molecular weight plastic polymer degradation. Such approaches are necessary for enzymatic degraders of high molecular weight plastic polymers to be differentiated from organisms only capable of degrading the more labile carbon within predominantly amorphous plastics, plastic monomers, additives or fillers.

Global plastic pollution

The first plastic to be produced in commercial quantities, Bakelite, was invented in the early 1900s. A scarcity of resources and a need to enhance technologies following the First World War drove the development of new and improved synthetic materials, including plastics. Plastics now constitute a large and diverse group of materials made from combinations of synthetic and semi-synthetic polymer materials, frequently incorporating additives which aid the manufacture and performance of the final product, such as plasticisers, antioxidants and flame retardants [ 1 ]. Plastics are predominantly derived from fossil fuels (e.g. oil or natural gas), although they may also be made from renewable resources (e.g. ‘bio-based’ plastics derived from corn starch or sugar beet); plastics such as polyethylene terephthalate (PET) may be synthesized from either source and are sometimes referred to as ‘drop-in’ plastics. With the onset of mass consumerism in the 1960s and a move away from the use of traditional natural materials to more versatile plastics, plastics are now an integral part of our everyday lives. Plastic production has increased exponentially since the 1950s, with an estimated 8300 million metric tonnes of virgin plastic being produced to date and an expected annual production rate of 1100 t by 2050 [ 2 ].

Despite the large variety of polymers available, just eight make up 95% of all primary plastics ever made, with polypropylene and polyethylene comprising 45% of global production [ 2 ]. The primary use of plastic is for packaging (36%), followed by use in building and construction (16%) [ 3 ]. Currently, the dominant polymer types are entirely fossil-fuel based and are not biodegradable in a timescale relevant for their end-of-life management. Fossil-fuel based biodegradable polymers such as polycaprolactone (PCL) and polybutylene adipate terephthalate (PBAT) are not currently used at large scale. In fact, less than 1% of polymers are bio-based, and of those 44.5% are ‘drop-in’ polymers which share the same properties of their fossil fuel-based versions, i.e., they are considered non-degradable [ 4 ]. Of the almost 360 million tonnes of plastic produced annually, only a small fraction (~ 1%) is bio-based [ 4 ].

At their end-of-life, there are essentially three fates for plastics: recycling; incineration and discarding. To date, end-of-life management of plastic products has not kept pace with rapid increases in production, resulting in widespread environmental contamination. Globally, it is estimated that only 10% of plastics are recycled and 14% incinerated; the remaining 76% goes to landfills or enters the natural environment [ 2 ]. Recent modelling estimates that under current rates of loss, with no changes to management practices and in conjunction with the anticipated increase in production, 710 million tonnes of plastic waste will have cumulatively entered the environment by 2040 [ 5 ]. Whilst large plastic waste normally comes to mind when discussing leakage to the environment, the natural wear and tear of items, such as ropes, clothing and tyres, sheds small fragments during use, facilitating the passive transport of smaller plastic fragments into the environment. These fragments, when less than 5 mm are referred to as microplastics, or nanoplastics if less than 1 μm [ 6 ]. Microplastic leakage is expected to increase by 1.3 – 2.5 times by 2040 under a business-as-usual scenario and equates to approximately 3 million trillion pieces [ 5 ]. This widespread ingress of plastics into the environment means they are distributed across the globe in many different forms and in all ecosystems so far investigated; from rivers and streams [ 7 , 8 ] to deep ocean trenches [ 9 , 10 ], mountain tops [ 11 ], and from the tropics [ 12 ] to the poles [ 13 ].

Microbial impacts of global plastic pollution

The recent death of a Cuvier’s beaked whale in the Philippines with 40 kg of plastic waste in its stomach [ 14 ] and the necropsy of a young sperm whale on a Scottish beach yielding 100 kg of refuse [ 15 ] caught global media attention and scientists continue to report impacts of plastic waste on a wide range of species [ 16 – 18 ]. More than 800 animal species are already shown to have been affected by plastic pollution, and with an increasing number, from detritivorous sea snails [ 19 ] to apex marine predators [ 20 , 21 ], being found to have internalised plastics. Globally, Wilcox, et al. [ 22 ] predict that as many as 90% of all seabirds ingest plastics. Post-mortem images of plastics spilling from the guts of dissected marine animals are causing us to reconsider unsustainable plastic use, yet the impacts of plastic pollution on most smaller organisms remain less well studied. Certainly, negative consequences of plastics have been reported for meiofauna such as Daphnia magna [ 23 ] and Caenorhabditis elegans nematodes [ 24 ], largely attributed to toxicological impacts, or blockage of the digestive system and related reductions in feeding rates. In contrast, the impact of plastics on environmental communities of microorganisms is rather less well researched.

The term ‘microbiome’ describes the combined genetic material, or community, of microorganisms inhabiting a particular environment. While researchers continue to explore diverse microbiomes, including of soil, marine, freshwater, atmosphere and subsurface environments, the term ‘microbiome’ is perhaps predominently used to describe research into the microbiome of the gastrointestinal tract (the so-called ‘gut microbiome’). Since environmental plastics can concentrate in the digestive tracts of organisms from diverse trophic levels [ 25 – 27 ] they have the potential to impact the gut microbiome. However, due to their widespread environmental distribution, impacts of plastic pollution further extend to the microbiomes of diverse, non-host associated environments (which hereafter we refer to as the ‘environmental microbiome’). The direct impact of plastics on gut and environmental microbiomes are multiple (Fig.  1 ). (i) Some plastics and/or their associated additives provide organic carbon sources metabolizable by certain microorganisms. However, the microbial degradation of most plastics is restricted to only a few taxa [ 28 ], remains slow, and in many cases is unproven or disputed. Indeed, there remains a paucity of evidence for the microbial degradation of dominant plastic polymers, including polypropylene, polystyrene, polyethylene, nylon and polyvinyl chloride [ 29 ]. For these reasons, the impacts of plastics on microbial communities as a source of additional carbon are likely to be minimal, particularly in natural environments where alternative labile carbon and energy sources dominate. A notable exception to this may be following plastic consumption by certain insects where microbial degradation is postulated to be enhanced via ‘prior-processing’ by enzymes present within the gut [ 30 ]; this hypothesis however remains unproven. (ii) To a large degree, pure plastic polymers are chemically benign, having little toxic impact . However, industrial plastics contain additives including flame retardants (e.g., polychlorinated biphenyls and polychlorinated naphthalenes), plasticisers (e.g., bisphenol A) and UV stabilisers (e.g., benzotriazoles), some of which are demonstrated to impact microbial community composition and functioning. For example, plastic leachates from high-density polyethylene (HDPE) and polyvinylchloride (PVC) exert toxic effects on Prochlorococcus spp. , impairing cell growth and population density in a dose-dependent manner [ 31 ]. Prochlorococcus is among the most numerous of photosynthetic organisms on Earth [ 32 ], responsible for perhaps ~ 10% of ocean net primary production [ 33 ]; in this regard, plastic pollution has demonstrated potential to impact major global microbial processes. Consumption of plasticisers including bisphenol A [ 34 ] may similarly cause dysbiosis of the gut microbiome, impacting host health. (iii) Plastics may also change microbial communities by impacting rates and extents of dispersal, since they provide a surface for microbial attachment and thereby can aid the transport of microbial cells, including pathogens, both around the globe and into the gut. In comparison to these direct impacts of plastics on microbiomes, far less is understood about their indirect impacts. Plastics and their additives can impact the health of host organisms with consequences for the gut microbiota that is intrinsic to the wellbeing of higher animals [ 35 ].

Schematic highlighting the diversity of direct and indirect impacts of plastics for gut and environmental microbiome communities and possible microbial solutions for the remediation of plastic waste

In this review, we highlight recent knowledge on the direct and indirect impacts of plastics on the health and functioning of environmental microbiomes, including of the gut. We further consider how the impacts of plastics may be mitigated and also manipulated to enhance both rates and extents of plastic degradation.

Impacts of plastics on the gut microbiome

Plastics cause a variety of undesirable mechanical, chemical and biological impacts on the species that ingest them. The consumption of plastics, either directly or via trophic level transfer [ 25 ], has multiple direct consequences, reducing appetite, impacting feeding activity and decreasing body weight [ 36 ], fitness [ 37 ] and fecundity [ 38 ]. In severe cases, the accumulation of large plastic masses may block the gastrointestinal tract; this has been recorded as a cause of death in diverse species including cetaceans [ 39 , 40 ], turtles [ 41 ] and birds [ 42 ]. Smaller fractions of plastic may also bioaccumulate in the body, mostly in the gut, although translocation of plastics via the haemolymph and haemocytes of filter feeders is reported [ 26 , 43 ], including to organs such as the liver and kidneys [ 44 , 45 ]; this implies an ability for microplastics to cross the gut epithelial lining following ingestion and enter the circulatory system. Avio, et al. [ 43 ] explored the impact of polyethylene and polystyrene microplastics on the Mediterranean mussel ( Mytilus galloprovincialis ). Following 7 days of exposure to the plastic, histological analysis revealed aggregates of plastic in the intestinal lumen, epithelium and tubules. Further, increased DNA strand breakages provide evidence of genotoxic impacts, possibly caused by the greater production of reactive oxygen species (ROS) in response to microplastics. Nucleotide-binding oligomerization domain-like, or NOD-like receptor signalling pathways were enriched in M. galloprovincialis exposed to microplastics; these receptors recognise pathogenic factors entering the cell via phagocytosis and activate inflammatory responses. These findings support a growing body of evidence that micro- and nanoplastics cross biological barriers to promote immune and inflammatory responses [ 45 , 46 ]. Where microplastics impact host immunity, this can further cause changes in gut microbial community composition and functioning. Oxidative states caused by inflammation can encourage the dominance of more resistant bacterial groups and, if associated with a rise in anaerobic respiratory terminal electron acceptors, may support the growth of anaerobic taxa such as members of the Enterobacteriaceae [ 47 ]. The gut microbiome influences not only the host immune system, but also contributes to digestion and the provision of essential nutrients [ 48 ], the degradation of harmful substances [ 49 ] and pathogen control within the gut [ 50 ]. The consumption and translocation of microplastics among bodily tissues therefore has far reaching consequences for the homeostasis normally maintained between a host and its microbiome.

While the physical presence of plastics demonstrably impacts the microbiome-gut-immune axis, additives which leach from plastic polymers have further consequences. Plasticisers are the largest group of plastic additives [ 51 ], particularly phthalates which may concentrate in bodily tissues to induce multiple adverse effects. For example, diethyl-hexyl phthalate (DEHP) causes antiestrogenic properties in fish hindering the development of reproductive organs [ 52 ], presumably due to competition with endogenous oestrogens for the receptor, and dibutyl phthalates delay gonad development and functioning in mammals [ 53 ] and amphibians [ 54 ]. The presence of bisphenol A (BPA) in the environment is predominantly due to it being a constitutive monomer of polycarbonate plastics, although it is also commonly added to PVC as a plasticiser. BPA has feminising impacts in fish, reducing male sperm quality, delaying and inhibiting ovulation in females [ 55 ] and in cases of high-concentration exposure, can induce intersex states [ 56 ]. Impacts on many other organisms are reported; BPA influences thyroid functioning and larval development in amphibians [ 57 ], early embryo development in marine bivalves [ 58 ] and reproductive birthweights and altered oestrous cyclicity in mammals [ 59 , 60 ]. Plastics also adsorb organic pollutants such as polychlorinated biphenyl (PCB) from their environment [ 61 , 62 ]; these contaminants may be transferred to the biological tissues of organisms such as birds following plastic ingestion [ 51 ]. While concentrations of plastic-associated contaminants are unlikely to be a major contributor to environmental concentrations of contaminants such as PCBs [ 63 ], a variety of plastic-associated compounds must be considered when assessing the impacts of plastic pollution on host-microbiome interactions [ 64 ].

The impacts of plastic additives on the gut microbiome remains little explored, although Adamovsky, et al. [ 65 ] assessed the consequences of environmentally relevant concentrations of the widely used plasticiser DEHP [ 66 ] on zebrafish. DEHP caused dysbiosis of the gut microbiota [ 67 ], and assessment of the gastrointestinal transcriptome revealed the up-regulation of T cells thought to play key roles in pathogen neutralisation by maintaining the integrity of the intestinal epithelia, while downregulating neuropeptide Y, a hormone which can modify immune activity by regulating T cell function. Analysis of the gut microbiome implicated several microbial metabolites that may contribute to immune and intercellular communication, including decreased L-glutamine in males and D-fructose 6-phosphate in females. Following DEHP exposure, Adamovsky, et al. [ 65 ] thereby identified the impact of microbial bioactive metabolites on host immune system dysregulation. Further negative impacts are reported. For example, the abundance of Mogibacteriaceae , Sutterella spp. and Clostridiales bacteria is increased within female mice exposed to BPA [ 68 ], presumably due to disrupted regulation of the sex hormones testosterone and oestrogen, implicating BPA for causing sex-dependent changes in the gut microbiome. The exposure of animals to plasticisers and plastic precursors including BPA are confirmed to impact intestinal microbial profiles in multiple studies [ 69 – 71 ], sometimes favouring microbial markers of dysbiosis such as a community dominance by Proteobacteria [ 72 ]. Nevertheless, understanding of cause and effect in host-microbiome interactions remains limited.

As we will later describe, microplastics are potential vectors of pests and pathogens around the globe via ocean currents, but so too may they vector pathogens into the gut. Microbial attachment to plastic particles can enhance both microbial dispersal and survival, as biofilms offer protection from environmental stress and enhanced opportunities for the sharing of beneficial traits via horizontal gene transfer. Pathogens such as Vibrio parahaemolyticus, which causes septicaemia and gastroenteritis in humans, have been identified in marine plastic-associated biofilm communities [ 73 ] and ingestion of such organisms hitchhiking on plastics might cause disease. However, even if not pathogenic, ingested organisms can influence gut community composition if they are capable of competing for resources within the gut [ 74 ]. Although the rich taxonomic and functional diversity of ‘plastisphere’ microbial communities has recently been unveiled [ 75 ], the role of plastics for microbial dispersal and colonisation of the gut remains poorly studied and understood.

Impacts of plastics on the environmental microbiome

In terrestrial environments, the mere presence of plastics exerts physical impacts directly impacting microbial communities. For example, agricultural plastic mulch films applied to enhance short-term crop productivity cover perhaps ~ 20 million hectares of farmland worldwide [ 76 ] and are a significant source of terrestrial plastic contamination [ 77 ]. While most research has focused on the impact of synthetic plastic films, the microbial consumption of biodegradable plastics is noted to have profound impacts on soil microbial communities [ 78 ]. Once embedded in the soil, plastics impact soil-water interactions by increasing water content [ 79 ], a major determinant of soil microbial community composition and functioning [ 80 , 81 ]. By altering the availability of water, the physical impact of plastics on the soil environmental microbiome may be substantial [ 82 ]; the consequence of other physical impacts, such as increased shading by plastics which has been hypothesised to reduce aquatic photosynthesis, remain largely unsupported [ 83 , 84 ].

The presence of plastic has direct chemical consequences for environmental microbial communities. Readily biodegradable plastics such as polylactic acid (PLA) contribute available carbon and in some cases significantly increase microbial biomass and enzyme activity [ 85 ]. The presence of such plastics in soils alter community composition, enriching the abundance and activity of certain taxa (e.g., members of the Ascomycota fungi [ 86 ]). The impact of more recalcitrant plastics remains less well understood, although even where degradation is slow, plasticising agents and additives such as phthalate acid esters may nevertheless leach, reaching elevated concentrations within receiving environments [ 87 ] and cause significant shifts in microbial community composition, abundance and enzyme activity [ 88 , 89 ]. Although plastic additives are not always observed to impact environmental microbiomes at environmentally relevant concentrations [ 90 ], the sheer diversity of plastic additives used [ 91 ] means their impacts are yet to be fully understood. Of particular interest, Tetu, et al. [ 31 ] investigated the consequences of plastic leachate from HDPE bags and PVC matting on marine Prochlorococcus and confirmed that exposure to even the lowest dilution (approximately 1.6 g L − 1 and 0.125 g L − 1 , respectively) of HDPE and PVC from 5-day old leachate impaired Prochlorococcus growth . Further, the transcription of genes associated with primary production was highly impacted, indicating that exposure to leachate from common plastic items has the capacity to impair the photosynthesis of the most dominant marine organisms.

Through the ubiquitous interactions between microorganisms and macroscopic plants and animals [ 92 , 93 ], plastics and their associated compounds exert multiple indirect biological impacts on environmental microbiomes. For example, plants can be impacted as they take up plastics such as polystyrene via their roots, altering root length, weight and oxidative stress responses, possibly by the disruption of cell wall pores and cell-to-cell connections used for nutrient transport [ 94 , 95 ]. Plant taxonomy and health play an important role in shaping soil and rhizosphere microbiomes, impacting the quantity and quality of root exudates [ 96 ] and the potential of plants to recruit specific members of the soil microbiome and promote the expression of genes, including those required for chemotaxis and biofilm formation [ 97 ]. Where observed, the impacts of plastics on the composition and health of plant and animal communities will likely have significant influences on environmental microbiomes, but to date insufficient evidence exists to suggest a strong link. Impacts on macroorganisms are rarely detected at environmentally relevant concentrations of microplastic; Judy, et al. [ 98 ] found no evidence of any impact of microplastics on wheat seedling emergence and production, or on the mortality or behaviour of earthworm and nematode populations.

While much research has focused on the impacts of plastics on microbial communities in situ , environmental plastics also influence rates and extents of microbial dispersal among environments. Buoyant plastics such as polyethylene, polypropylene and polystyrene, are transported over long distances by winds and oceanic currents [ 99 ] whereas non-buoyant plastics such as PET and PLA may act as a vector to transport surface-associated microbes to deeper water [ 100 ]. Microbial groups, including toxic microalgae [ 101 ] and potential human [ 75 ] and animal pathogens [ 102 ] have been detected associated with marine and freshwater plastics [ 73 , 103 ] along with diverse antibiotic-resistant taxa [ 104 ]. Plastics are further postulated to vector pathogens through wastewater treatment plants [ 105 ] and pest species via ballast water [ 106 ]. Microbial communities colonising environmental plastics likely aid larval settlement and colonisation by species including bryozoans and polychaete worms, thereby assisting the movement of invasive marine macroorganisms around the globe [ 107 ]. Thus, in addition to supporting or retarding the growth of certain taxa, environmental plastics likely play significant roles in the dispersal of both microbes and higher organisms across diverse spatial scales and habitat types. Interestingly, the microbial colonisation of plastics can also impact particle buoyancy and transport [ 108 , 109 ].

Assessing diverse plastisphere communities via amplicon and metagenome DNA sequencing

The development of molecular methods, including high-throughput DNA sequencing technology, is increasing our knowledge of the diverse nature of plastic-associated microbiomes. Although no taxa are known to only, or even to predominantly colonise plastic surfaces, multiple studies have demonstrated how the microbiomes of plastic debris differ from those present in the surrounding environment [ 110 – 113 ], with an overrepresentation in the plastisphere of bacterial phyla such as the Proteobacteria, Bacteriodetes [ 114 ] and Cyanobacteria [ 115 ] and fungi such as Chytridiomycota [ 113 ]. Nevertheless, with studies on the community composition of plastisphere microbiomes still in their infancy, it remains unclear the extent to which a core plastisphere community exists and the degree to which this differs from comparable microbiome communities in the same environment.

The specificity of plastisphere communities has been investigated in comparison to communities growing on inert surfaces such as glass and ceramic with varying results. A study by Oberbeckmann, et al. [ 116 ] using 16S rRNA gene amplicon sequencing for taxonomic analysis found no significant difference between the pelagic microbial communities associated with PET plastic bottles and glass microscope slides (as a control) deployed for 5-6 weeks. Pinto, et al. [ 117 ] also found that the overall community assembly on glass was similar among biofilms developing on HDPE, LDPE and PP over a period of up to 2 months, with families such as Flavobacteriaceae, Phyllobacteriaceae, Planctomycetaceae and Rhodobacteraceae being highly abundant across all surfaces. Such findings (also see Dang, et al. [ 118 ]) lead us to assume that there may be no specific plastic-associated communities. However, despite finding no differences in the total composition of communities growing on glass, HDPE, LDPE and PP (noting that significant differences were however observed for communities on PVC), Pinto, et al. [ 117 ] identified a subset of these communities incubated after immersion into seawater for up to 2 months, which was nonetheless responsive to the characteristics of individual plastic polymers or their additives (also see Ogonowski, et al. [ 119 ] and Kelly, et al. [ 7 ]). A higher relative abundance of the bacterial family Rhodobacteraceae discriminated communities growing on HDPE and Sphingomonadaceae for communities growing on LDPE, as compared to glass. Using a longer period of incubation, Kirstein et al. [ 120 ] found that after 15 months in a natural seawater flow-through system, biofilms from HDPE, LDPE, PP, PS, PET, PLA, styrene-acrylonitryle (SAN), polyurethane prepolymer (PESTUR) and PVC were significantly different to communities formed on glass. While communities on PVC were noticeable for having a high abundance (> 5%) of the bacterial genus Flexithrix, differences in the abundances of other plastic-specific taxa were largely attributed to variation in the presence and abundance of less dominant OTUs, suggesting that rarer species form specific associations with certain plastic types [ 121 ]. Also supporting the notion that less dominant members of the community may respond more specifically to the presence of different plastics, Erni-Cassola, et al. [ 122 ] demonstrated that during two-day incubations, weathered LDPE was enriched with a distinct community (particularly members of Roseobacter-, Oleiphilus- and Aestuariibacter- like taxa) from untreated PE and glass. However, this distinction was not detectable after 9 days, suggesting that substrate-specific microbes present in the plastisphere are quickly masked as the community matured and putative plastic-specific taxa were outnumbered. Interestingly, while significant differences in microbial community composition are not consistently reported among communities developing on different plastics, different plastic colours have recently been implicated as a significant determinant of plastisphere microbial community structure and functional diversity [ 123 ].

To date, a majority of studies assessing the formation and development of plastisphere communities have been conducted in the laboratory using different types of plastic of various condition (e.g., from ‘virgin’ plastics specifically manufactured for a study [ 124 ] to post-consumer plastics such as discarded bags and PET bottles [ 116 ]). Considering the longevity of plastic debris in the environment, the relatively short lengths of most lab-based studies may not be enough to explore the full degradative potential of the plastisphere microbiome. Environmental plastics hosting mature plastisphere microbiomes provide an alternative way to investigate the many factors that can influence plastisphere formation, such as plastic composition, age and condition. However, characterisation of aged microplastics, which dominate the marine plastisphere in terms of abundance, is often restricted as the biomass recovered from environmental microplastics is frequently very low, limiting abilities to recover sufficient nucleic acids for sequence analysis. As a consequence, there remain many unanswered questions regarding the plastisphere of aged environmental microplastics in particular.

As our knowledge of microorganisms present in the plastisphere is growing, there are still important questions that remain unanswered. (i) Which microorganisms act as pioneer species when the plastic is first introduced into the environment, and do the priority effects of early colonisation affect the overall composition and metabolic potential of the microbial community later on? These questions are of particular importance since the enrichment of plastic-degrading organisms may predominantly occur during early stages of colonisation, before the labile substrates generated from weathering are depleted and these plastic-specific microbes are dominated by more generalist biofilm-dwelling taxa [ 122 ]. (ii) Does there exist a core global community of plastic-degrading taxa, or do they exhibit substantial geographic or habitat-specific biogeography? (iii) If core members of the plastisphere vary in abundance between plastic types and biofilm maturity, can the presence and abundance of certain microorganisms indicate the approximate type and age of plastic debris? Answers to these questions will assist our ability to identify plastic-specific microorganisms from different regions, biomes, on different plastics and at different stages of plastic aging and degradation. Additionally, such knowledge likely increases our ability to use microbial community DNA to inform on the environmental impact of plastics (for example by adopting the approach of Hermans, et al. [ 125 ]).

As highlighted by Wright, et al. [ 126 ], many studies have characterised the plastisphere through taxonomic analyses [ 112 , 117 , 121 , 122 ], however, there remains a lack of knowledge surrounding the functional potential of these communities. Bryant et al. [ 115 ] were among the first to explore the metabolic potential of the plastisphere microbiome using shotgun metagenomics, hypothesising that the genomes of plastic-associated taxa would be more distinct and exhibit increased metabolic activity compared to free-living bacteria in the surrounding marine water. Compared to those of the picoplankton community, their study revealed an increased abundance of genes encoding for chemotaxis and nitrogen fixation as well as several putative genes for xenobiotic biodegradation in plastic-associated communities. This included a gene encoding for 2,4-dichlorophenol 6-monooxygenase, a hydroxylase associated with the degradation of chlorinated aromatic pollutants [ 127 ] sometimes produced from polymer and plastic additive pyrolysis [ 128 ]. Similarly, the study revealed an increased abundance of multiple genes encoding for ring-cleaving enzymes, such as protocatechuate 3,4-dioxygenase and particularly homogentisate 1,2-dioxygenase, previously linked with styrene and polycyclic aromatic hydrocarbon degradation [ 129 ]. Whilst Bryant, et al. [ 115 ] were unable to confirm if microbes within the plastisphere are able to degrade the plastic polymer, the increased abundance of genes encoding for the degradation of several xenobiotics may assist identification of new plastic-degrading enzymes, and also the taxa expressing and utilising these enzymes. In common with previous studies, Pinnell & Turner [ 130 ] found the community composition of fossil fuel-derived PET-associated biofilms to be indistinguishable from those growing on ceramic beads deployed at the sediment-water interface of a coastal lagoon; in contrast, microbial communities associated with bio-based PHA pellets were dominated by sulphate-reducing organisms. Metagenomic analysis of the bioplastic-associated communities revealed substantial phylogenetic diversification of one depolymerase in particular, polyhydroxybutyrate (PHB) depolymerase, alongside an almost 20-fold increase in abundance of the depolymerase genes, suggesting they are widely distributed within the biofilm. An increased abundance of genes associated with sulphate reduction and plastic degradation, such as depolymerases, esterases and sulphate reductases, were also reported. Thus, while bio-based plastics continue to be perceived as an environmentally friendly alternative, if sedimentary inputs are large enough, the authors speculate that microbial responses could impact benthic biogeochemical cycling through the stimulation of sulphate reducers.

It is likely that communities work together to access plastic-derived carbon; the genes encoding for the degradation of alkanes, for example, are distributed among diverse assemblages of hydrocarbonoclastic organisms [ 131 ]. A greater understanding of the dynamics of plastic-associating communities may be achieved by determining co-occurrence patterns and associations among different organisms and genes. Toxic and poorly labile carbon substrates have been observed to strongly favour facilitation among microbial species such that they can each grow and degrade these substrates better in order to survive [ 132 ]. Where taxa or gene products are presumed to play a beneficial role in plastic degradation, correlated increases in their abundance across multiple samples as indicated by network analysis (e.g. see Gatica, et al. [ 133 ]) might identify other organisms and molecular pathways that could benefit from the community response to plastic contaminants.

Mitigation of plastic pollution by the gut microbiome

Recently, several insect species (particularly the larvae of darkling beetles, wax moths and meal moths) have garnered interest for their ability to consume and degrade a diversity of plastic polymers. For example, larvae of the Indian meal moth Plodia interpunctella can ingest and appear capable of degrading polystyrene [ 134 ] as do larvae of yellow and giant mealworms Tenebrio molitor and Zophrobas morio , respectively [ 135 , 136 ]. Larvae of the greater [ 137 ] and lesser wax moths ( Galleria mellonella and Achroia grisella [ 138 ]) are similarly reported to degrade polyethylene and polystyrene, respectively. Isotope analysis provides evidence that carbon from plastics such as PE is incorporated into the biomass of invertebrates [ 139 ]. Despite the findings of these and other studies, it nevertheless remains uncertain the extent to which either the higher organism or its associated microbiome contribute toward plastic polymer degradation. Further, the extent to which these biodegradative processes may be accelerated by synergistic effects of the host-microbiome remains unclear (Fig.  2 ).

Evidence for a role for insects, host-associated microbes, or host-independent, free-living microbes in plastic degradation. Degradation of the plastic polymer may be detected by a variety of methods, including: [i] mass loss of plastic such as clear zone development around colonies on plastic-infused/overlaid agar, [ii] altered plastic surface properties (e.g., visible by scanning electron microscopy) and [iii] generation of degradation products (e.g., CO 2 , polymer metabolites detected by Fourier-transform infrared spectroscopy or high-performance liquid chromatography)

Many organisms consume plastic incidentally and gain no nutritional value from its consumption; plastic has been found in abundance within the guts of diverse organisms from seabirds [ 22 ] and fish [ 140 ] to marine and freshwater worms [ 36 , 141 ] and zooplankton [ 142 ]. Although the ingestion of plastics by species including the common earthworm Lumbricus terrestris is associated with reductions in plastic size distribution [ 143 ], in many cases, demonstration of plastic degradation, e.g. by conversion to CO 2 or incorporation of plastic-associated carbon into animal biomass, is unsubstantiated [ 144 ]. Similarly, the ‘consumption’ of plastics by mealworms and wax moth larvae has gained much attention [ 30 , 145 ], but confirmation of plastic degradation by the hosts’ gut-derived enzymes, independent of the hosts’ microbiome, requires further confirmation [ 146 ]. In most cases, it remains to be seen whether the host derives any nutritional benefits from plastic as a source of energy; without stronger evidence of more complete degradation in the gut, plastic fragments may merely be generated via mechanical processes (e.g. chewing) and ejected into the environment. To confirm plastic degradation by macroinvertebrates, studies in germ-free organisms (i.e., those lacking a microbiome) are desirable, noting the physiological homeostasis of organisms such as T. molitor are impacted by related changes in digestive enzyme expression by axenic cultures [ 147 ]. Another approach is to track the fate of radiolabelled (e.g. 13 C, 14 C) plastic polymer via incorporation into the cellular biomass or respiration products of consumer invertebrates [ 139 ], preferably in the absence of host microbial taxa to also eliminate the possibility of trophic carbon transfer. The lack of evidence to date for plastic degradation by germ-free larvae instead supports that microbiota are important drivers of plastic degradation within the invertebrate gut.

Since diverse putative plastic-degrading microbial taxa have now been described, including isolates from gut microbiota [ 28 ], it is hypothesised that the enzymes of gut-associated microbial taxa, rather than the enzymes of the host per se, perform most, if not all, plastic degradation by plastic-consuming invertebrate taxa. In a series of experiments, Cassone, et al. [ 148 ] provide multiple lines of evidence for the degradation of LDPE by the intact microbiome of G. mellonella larvae. The larvae of G. mellonella readily consume beeswax, which in some aspects is similar to plastics such as PE, being comprised of a diverse mixture of long-chain hydrocarbons. Hence, plastic consumption propensity may be related to the structural or chemical similarity of plastics to their preferred food source. PE-fed caterpillars had a far greater abundance of gut-associated microorganisms as compared to starved individuals, or even to organisms fed a natural diet of honeycomb, suggesting their microbiota could benefit from the abundance of PE in the gut. Antibiotic-treated caterpillars fed PE also excreted only half the concentration of ethylene glycol compared to untreated animals. Since ethylene glycol is a putative by-product of PE metabolism [ 30 ] this was used to imply a direct role of the gut microbiome for PE degradation. The inhibition of plastic depolymerisation following antibiotic treatment has now been observed in numerous studies, indicating that the host organism alone is poorly able to utilise plastic as a carbon or energy source, or is at least in part reliant on its microbiome as a source of plastic-degrading enzymes [ 135 , 136 , 144 , 148 ]. Providing further evidence for a microbial role in plastic degradation, Cassone, et al. [ 148 ] isolated and grew bacteria from the gut (identified as Acinetobacter sp.) on carbon-free media, supplemented with PE fragments. A further observation was that the Acinetobacter sp. was only capable of degrading plastics at a very slow rate when isolated from the gut, providing evidence that plastic degradation is maximised by synergisms occurring between the host and its gut microbiome community, although the importance of community microbial interactions cannot be disregarded. Nevertheless, the extent to which the larvae impact the structure of the plastic polymer or associated additives, or enhances beneficial functional attributes of its gut microbiota currently remains unclear.

Prior to the study of Cassone, et al. [ 148 ], multiple authors had already isolated putative plastic-degrading bacteria from the insect gut microbiome. Yang, et al. [ 144 ] isolated the bacterium Exiguobacterium sp. Strain YT2 from the gut of styrofoam-fed mealworms and demonstrated its ability to grow on polystyrene film as a sole carbon source, associated with changes in the surface topography and hydrophobicity of the plastic. Mass loss of polystyrene combined with decreases in molecular weight and the release of water-soluble degradation products were used as further evidence to highlight the capacity for gut-associated microbes to degrade plastics (noting that Danso, et al. [ 29 ] question if sufficient evidence is available to confirm degradation of the high-molecular weight polymer, i.e. the polystyrene itself, rather than styrene monomers incorporated within the polymer matrix). Similar studies implicate Aspergillus flavus, Bacillus sp. YP1 and Enterobacter asburiae YT1 isolated from insect gut microbiomes as being capable of PE degradation [ 134 , 149 ]. While such findings identify a possible role for gut-associated microbes to degrade plastic, organisms isolated from non-host environments are similarly capable of plastic degradation and could be exploited for their biodegradation capacity.

Mitigation of plastic pollution by the environmental microbiome

The first evidence that free-living environmental taxa contribute to plastic degradation was only published circa 30 years after the first commercial plastic production, in 1974, when Fields, et al. [ 150 ] showed that the fungus Aureobasidium pullulans was capable of PCL degradation. Since then, the number of microorganisms suggested as capable of plastic biodegradation has increased considerably. A recent study by Gambarini, et al. [ 28 ] reports over 400 publications describing the degradation of 72 different plastic types by 436 species of fungi and bacteria. Presumptive plastic-degrading microbes identified to date belong to five bacterial and three fungal phyla. Among the bacterial phyla, Proteobacteria ( n  = 133), Actinobacteria ( n  = 88), and Firmicutes ( n  = 60) have the greatest number of reported species, while Bacteroidetes ( n  = 3) and Cyanobacteria ( n  = 2) have far fewer. The fungal phyla include Ascomycota ( n  = 118), Basidiomycota ( n  = 19), and Mucoromycota ( n  = 13) (Fig.  3 ).

Number of putative plastic-degrading organisms reported by Gambarini, et al. [ 28 ], classified at the level of phylum level. The number following the phylum name represents the number of species from that specific phylum that are reported as plastic-degraders

As outlined earlier, a small number of plastic-degrading microbes have been isolated from plant- and animal-associated microbiomes [ 149 , 151 , 152 ]. However, most isolates reported in the literature were derived from soil [ 153 , 154 ] or from waste processing sites such as composting facilities [ 155 ] and landfills [ 156 ]. An additional source comprises bacteria and fungi already deposited in culture collections [ 157 ]. All major synthetic polymers have species reported to degrade them, for instance PE [ 158 , 159 ], PET [ 160 , 161 ], PP [ 162 ], PS [ 163 ], PU [ 164 ] and PVC [ 165 ]. However, the strength of evidence for degradation varies by plastic type. To date, PET biodegradation has been studied the most comprehensively. A notable example includes the PET-degrading bacterium, Ideonella sakaiensis , isolated from sediment in the vicinity of a Japanese bottle recycling plant [ 161 ]. I. sakaiensis is the first organism for which the degradation of PET was well-described and the enzymatic degradation of PET elucidated, characterised [ 166 ] and enhanced [ 167 ]. Conversely, there is only weak evidence for the biodegradation of synthetic polymers such as nylon, PP, PS and PVC. For instance, nylon-oligomer biodegradation by the bacterium Agromyces sp. KY5R has been shown by Yasuhira, et al. [ 168 ] and the genes and corresponding enzymes responsible for the biodegradation activity have been identified; however, biodegradation of the plastic polymer (i.e. not just monomers and oligomers) is yet to be confirmed.

Bioprospecting for novel mechanisms of plastic degradation

Currently, there is a lack of information necessary to critically validate many reports of plastic degradation by microbial taxa or communities or to accurately reproduce the research. For instance, many reports provide no information regarding polymer composition and omit details of fillers and additives that may be present in polymer composites. Therefore, it is frequently not possible to differentiate between the microbial degradation of plastic polymers or their additives. The strength of the degradation evidence is also greatly dependent on the techniques applied, which can be divided into three main categories, those detecting: (i) changes in the polymer structure, (ii) physical loss of plastic mass and (iii) the generation of plastic metabolites. The strongest evidence of plastic biodegradation is likely achieved using a combination of techniques from all three categories. However, analysis of the dataset of Gambarini, et al. [ 28 ], which compiled data from 408 studies, revealed that of the microorganisms reported to degrade plastics, 48% of reports were based on assays relating to only one of these categories, 39% used techniques that covered two categories, and just 10% used techniques that covered all three (Fig.  4 ).

Percentage of studies using evidence for plastic degradation by microbial species based on: (i) changes in polymer structure (blue), (ii) physical loss of plastic mass (red), or (iii) detection of plastic metabolites (green), or these techniques in combination. Data were compiled using the

Most reports of plastic degradation by microbial isolates do not go on to explore the genes and enzymes responsible for the reported activity. In fact, only around 14% of the microorganisms reported to degrade plastic have the gene sequences conferring the degradation activity elucidated [ 28 ]. This represents a major shortcoming since knowledge of the relevant biochemical and molecular data provides the capability to advance the plastic biodegradation field enormously, allowing the search for new putative plastic-degrading genes in novel microbiomes by comparison to enzyme data banked in structural and molecular databases. Crucial information and procedures related to the reported plastic degraders are frequently missing or incomplete in the current literature, for example, the location and conditions of isolation of the plastic-degrading isolate, strength of evidence for degradation, accurate taxonomic classification, and a lack of deposited strains in culture banks. By not addressing these points adequately, reports of plastic degradation, possibly in a majority of studies undertaken to date, must be treated with caution.

To exploit the broad phenotypic diversity that may already be present in natural populations, future advances in plastic biodegradation will likely benefit from isolation of novel microorganisms from diverse microbiome communities. This calls for consideration of the sampling environment and likely growth requirements of organisms within the microbiome, the plastic type of interest and the empirical tests required to delineate growth-linked biodegradation of the polymer. By reviewing the current literature, we provide a ‘best practice’ workflow of methods necessary to describe the pathways of growth-linked plastic biodegradation, beginning with appropriately characterising the plastisphere microbiome and concluding with the identification of plastic biodegradation genes and pathways (Table  1 ).

Best practices for reporting microbial plastic degradation. We describe information, techniques, and practices that are critical to provide strong evidence for biodegradation, as well as steps necessary to maximise reproducibility of the findings

Based on protein mutagenic and structural analysis studies [ 166 ], alongside homology database searches [ 28 ], it is likely that certain microorganisms already possess plastic degradation genes but do not express them in situ, and/or derive energy from more readily utilisable carbon sources when available. By incorporating inert controls (e.g., glass or ceramic surfaces), we may be able to distinguish between genes acquired and expressed for the process of plastic-degradation, from those normally expressed in biofilm communities (i.e. including where plastic is not present). Yoshida et al., [ 161 ] demonstrated that I. sakaiensis possesses two genes encoding enzymes which degrade PET ( Is PETase and Is MHETase). However, they did not address if the Is PETase might be used by the organism for other functions, or whether it was being used in situ to degrade PET within the PET recycling plant from which the organism was originally isolated. Structural analyses of the Is PETase revealed that the enzyme has a wider active-site cleft compared to ancestral cutinase homologs [ 166 ]. Narrowing the active-site cleft via mutation of active-site amino acids improved crystalline PET degradation, indicating that the Is PETase was not fully optimised for PET metabolism. This, in conjunction with the initial isolations focusing on amorphous PET (1.9% crystalline) instead of the more crystalline PET abundant in bottle recycling plants (15.7% crystalline; Yoshida et al. [ 161 ]) suggests that the origin of the first I. sakaiensis isolate from a recycling plant might be coincidental.

Mere changes in polymer mechanical properties and physical structure, even when observed in concert with microbial biomass production, are insufficient evidence to confirm polymer biomineralisation by microbial isolates [ 172 ]. Physical losses of plastic mass should also be reported. Plastics can be incorporated into growth media as plastic films, powders or granules, and emulsifications. The first two approaches are primarily used to identify physical changes in polymer structure and the accumulation of biomass as first lines of evidence for plastic degradation (Table ​ (Table1; 1 ; Fig. ​ Fig.4). 4 ). Evidence of polymer degradation from plastic films or polymer granules predominantly requires changes in polymer roughness, the formation of holes or cracks, fragmentation or color changes, confirmed using visual methods such as scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) [ 173 ] or atomic force microscopy [ 174 ]. However, visual changes in surface structure, changes in plastic mass and mechanical properties do not provide direct evidence of biodegradation [ 175 ] because these physical changes cannot be distinguished from abiotic degradation. Where biodegradation is demonstrated it is likely that microbiomes work in conjunction with abiotic factors to impact the structural integrity of polymers [ 176 ]. Most polymers are too large to transverse the cell membranes and must be initially depolymerised (e.g. by heat, visible and non-visible spectrum light and oxygen) [ 177 ]. Additionally, measuring changes in the surface structure or molecular weight of plastics does not discriminate between the degradation of polymers or their additives [ 172 ]. Therefore, in addition to plastic film and granule-infused media, we recommended that biomass accumulation on plastic surfaces and changes to polymer structure should be accompanied by the detection of plastic metabolites to describe growth-linked biodegradation.

A common method for assessing microbial plastic metabolism is by observing clear zones in agar containing emulsified plastic [ 175 , 178 ]. However, emulsifications are usually limited to amorphous or lower molecular weight plastics while environmental waste plastics such as nylon, PE and PET typically have a higher molecular weight, limiting the analysis of these pollutant plastics. In addition, solvents and surfactants widely used to form plastic emulsions are themselves documented to be degraded by microorganisms [ 179 , 180 ]. Therefore, observation of clearance zones in culture media containing plastic emulsions should ideally be associated with other empirical tests, such as observations of incorporation of radiolabeled carbon from the polymer backbone into microbial biomass. Because plastic typically comprises the predominant or only carbon source in plastic metabolism assays, only small amounts of evolved CO 2 are typically required to be detected to indicate polymer metabolism [ 175 ]. In addition to CO 2 , other plastic metabolites hypothesised to be produced during plastic degradation (e.g. the production of mono-(2-hydroxyethyl) terephthalate during PET hydrolysis) may be identified using methods such as liquid/light Chromatography-Mass Spectrometry, which detects multiple compounds in a single analytical run [ 181 ]. This approach was employed to implicate the role of a putative depolymerase in PHB degradation by Aspergillus fumigatus [ 182 ]. Similarly, HPLC-mediated detection of the PET-degradation metabolites MHET and terephthalate provided evidence for Is PETase involvement in PET degradation [ 183 ]. These methods, combined with approaches employed to detect changes in polymer structure and metabolism (Fig. ​ (Fig.4) 4 ) provide powerful evidence for confirming plastic biodegradation.

Knowledge of genes known to be associated with plastic degradation provides a strong tool to identify new degraders and genes among microbiome communities. For instance, Danso, et al. [ 29 ] developed a hidden Markov model (HMM) to search genome and metagenome databases for the presence of potential PET hydrolases. The authors used the sequences from nine different enzymes with verified activity on PET-based substrates and identified 504 possible PET hydrolase candidate genes. Studies such as this, and the work of Gambarini, et al. [ 28 ], indicates a huge potential for mining molecular databases for plastic degradation-conferring genes (PDGs). One useful approach to verify PDGs experimentally is by heterologous expression of the microbiome-derived candidate genes in a host that lacks degradation capacity in the absence of the introduced gene, followed by confirmation of the plastic-degrading phenotype of the transformant. Heterologous expression in hosts such as Escherichia coli has been used to verify plastic degradation-conferring phenotypes of PDGs encoding putative PHB-depolymerases, esterases, cutinases, carboxylesterase and PET hydrolases from a wide variety of bacteria, and some fungi [ 29 , 184 – 186 ]. Overexpression in heterologous hosts is also a valuable tool for purifying high levels of enzyme for in vitro assays or studying enzyme crystal structure. Another approach is to disrupt or silence the candidate PDGs in the endogenous background and assess the effect this has on the plastic degradation phenotype. Mining metagenomes using the candidate gene approach does not inform on the discovery of completely novel determinants, or accessory factors that have not been previously described. Under this scenario, genotype-phenotype-based studies of individual degrading strains are still important to identify novel determinants, using methods such as DNA library screens in heterologous hosts, random mutagenesis or differential transcript expression. However, once PDGs are identified, interrogating metagenomes of closely related species for conserved alleles can inform on important residues and functional domains to exploit for genetic enhancement of plastic degradation traits.

Manipulating microbiomes to enhance rates and extents of plastic degradation

Different strategies may be employed to overcome the challenges of isolating microorganisms capable of efficient and/or fast plastic degradation. For example, higher temperatures can increase the flexibility of both amorphous [ 187 , 188 ] and crystalline domains of the polymer chain [ 189 – 191 ], thereby improving their accessibility to enzymatic attack [ 188 ]. In this regard, thermophile microbiomes represent a promising source of enzymes because they will likely be more thermostable. In one study, the most thermostable enzyme tested (a leaf-branch compost cutinase (LCC) obtained from an uncultured bacterium [ 186 ]) had the highest PET depolymerization rates at 65 °C [ 192 ]. Degradation rates were further increased after improving enzyme thermostability through site-specific mutagenesis. To date however, only ~ 10% of isolated plastic degradation studies report polymer degradation at temperatures ≥50 °C and only a small fraction (~ 0.5%) of these have been isolated from extreme environments such as hot springs, composts and anaerobic digesters [ 28 ]. There would appear to be significant scope for mining thermophile and extremophile microbiomes as a promising source of putative plastic degrading enzymes and microorganisms.

The higher genotypic and phenotypic diversity present in microbial communities compared with single microbial strains may mean that communities are more efficient degraders of xenobiotic pollutants [ 193 ]. As such, artificial consortia created by selecting a small number of plastic degrading microorganisms within an already existing consortium (i.e., using a top-down approach [ 194 ]), or combining separately isolated microbial strains (i.e., using a bottom-up approach [ 162 ]) may be a useful strategy for improving plastic biodegradation. Alternatively, directed mutagenesis to improve gene expression and enzyme function, along with metabolic engineering and synthetic biology tools, could be exploited to obtain more efficient plastic-degrading consortia. Specifically, the introduction or modification of interspecific microbial interactions (such as intercellular communication via metabolite exchange) could be used to create consortia with improved biodegradation traits [ 195 , 196 ]. Additionally, the segmentation of metabolic pathways among strains such that each organism produces an intermediate compound that can be used by the next organism in the pathway can be used to reduce the metabolic burden on any one organism. Because only limited information is available regarding genes and enzymes involved in plastic biodegradation [ 28 ], an improved understanding of degradation pathways by single strains and multi-strain co-degradation pathways is first required to facilitate this approach.

Conclusions

The impacts of global plastic pollution on microbiomes are diverse, ranging from the direct consequences of toxic leachates on microbial community health and activity to the indirect effects of plastics on host organisms and environments. Many hundreds of microbial species, genes and enzymes are implicated in plastic degradation. For a small number of particularly bio-based plastics, such as PLA, clear evidence is presented for their microbial degradation. However, for the majority of commercial plastics, evidence for microbial degradation remains weak, with studies failing to confirm microbial growth on the synthetic polymer. To ensure the correct identification of plastic-degrading taxa and enzymes, facilitating their improvement by environmental, biotic and genetic manipulation, multiple lines of evidence for plastic degradation should be presented. Ideally this will include evidence of changes in the polymer structure, mass loss and detection of degradation products, along with confirmation of the microbial strain and putative plastic-degrading enzymes and associated genes. Such details are essential for organisms and enzymes capable of plastic degradation to be reliably differentiated from those only capable of degrading the more labile carbon within predominantly amorphous plastics, plastic monomers, fillers and additives.

Abbreviations

Authors’ contributions.

All authors contributed to the research, writing and editing of this manuscript and provider their full consent for publication. The authors read and approved the final manuscript.

This work was conducted as part of the Aotearoa Impacts and Mitigation of Microplastics (AIM 2 ) project, in receipt of funds from a New Zealand Ministry of Business, Innovation and Employment (MBIE) Endeavour Fund Grant (C03X1802). Additional support was also provided via a University of Auckland Doctoral Scholarship (to SM) and doctoral scholarship funds provided via the George Mason Centre for the Natural Environment (to VG).

Ethics approval and consent to participate

No ethics approvals or consents were required.

Competing interests

No competing interests are declared.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

• Reference Manager
• Simple TEXT file

People also looked at

Perspective article, plastic pollution: about time to unify research methods and demand systemic changes.

• 1 Department of International Business, Norwegian University of Science and Technology (NTNU), Ålesund, Norway
• 2 Department of Geography, Norwegian University of Science and Technology (NTNU), Trondheim, Norway

The issue of plastic pollution is recognised as a pervasive and ubiquitous problem which can pose a threat to ecosystems worldwide and potentially affect human health. In this perspective, we selected the latest research that identifies potential impacts beyond individual species to draw attention on wider biogeochemical cycles and the most fundamental biological processes we all depend on, namely, breathing, feeding and carrying offspring. We highlight the need for uniform research methods, giving examples of protocols and indicator species that should be evaluated by the research community for their potential wide adoption. We stress the need for systemic changes and our role as scientific community to demand changes proportionate to the severity and implications of our findings. We further explore the push and pull mechanisms between researchers and policymakers in relation to the global environmental challenges such as plastic pollution. Finally, we recommend a path of action inspired by the global action taken to address the ozone layer depletion by banning chlorofluorocarbons (CFC).

Introduction

Marine plastic pollution or marine litter has become one of the most researched topics in marine pollution research as recently shown by Riechers et al. (2021) . The problem is so vast, so complex and so ubiquitous that research has flourished in an attempt to fill the numerous gaps left in this global jigsaw. When searching the literature on marine litter, one is left with a dizzying kaleidoscopic vision, as the more we get into the details, the more complex the problem appears. Each question gives rise to a plethora of other questions which, it seems, need answered before effective mitigation and prevention measures can be taken. This evokes the definition of a wicked problem, as summarized in Wagner (2022) for the case of plastic pollution. The issue is not less pressing within the terrestrial environment, but so far less researched. In this perspective article, we broadly sketch up the problem of plastic pollution on a large scale, looking at biogeochemical cycles and possible effects on ecosystems and physiological processes in humans and other species. We then reflect upon the lack of action, drawing on concepts of wicked environmental problems, leverage points, and the dynamic between researchers and policymakers. We conclude the article by tying together the different ropes looking at the historic success story of chlorofluorocarbons (CFC) to propose a path of action for the research community and policymakers.

Uncertainty: it depends on …

How does plastic flow? Where do marine debris come from and end up? How fast and under which circumstances does plastic get broken down into smaller pieces? What chemical pollutants are associated with plastic? What microbial communities grow on plastic to form the plastisphere ( Steer and Thompson, 2020 )? What are the effects, if any, of plastic ingestion by living organisms? What is the ecotoxicological threshold, for the polymers, associated colorants, chemical additives and “hitch-hikers” ( Kirstein et al., 2016 )? What are the pathways for their sorption into the food chain? And what other pathways exist for the sorption ( Khalid et al., 2021 ) of plastics and associated chemicals and pathogens? For each of these questions, the answer starts by “it depends … .” Indeed, it depends on the type of polymer, on the shape, the density, the size, the weight, the colour of the debris and type of additive ( Khalid et al., 2021 ). It also depends on the topography, weather conditions and within the marine environment, the currents ( Chassignet et al., 2021 ; Strand et al., 2021 ; Huserbråten et al., 2022 ). It depends on the species’ presence, on the behavior of individual organisms and on the concentration of plastic particles and their associated organic or inorganic compounds (e.g., Jacquin et al., 2019 ; Lopez-Martinez et al., 2020 ; Bonanno and Orlando-Bonaca, 2020 ; Khalid et al., 2021 ; Pirsaheb et al., 2020 ; Sönmez et al., 2022 ). And the list of variables goes on. A problem that is man-made, is totally escaping human comprehension. Indeed, the main challenge is to transcend local data and species-specific knowledge, to globally relevant science on the behavior and the effects of plastics and associated pollutants, that can inform policy-making.

Uniformity in research methods

At the center of this challenge is the lack of uniformity in research methods on plastic. This issue is due to the complexity and early stage of this field and to the ever-changing nature of the environment and the diversity of plastic types, sizes and associated organic and inorganic compounds. However, a consensus on methodologies is the essential first step to enable repeatability, better quality-assurance in review processes and, by extension, knowledge-building. This issue needs to be addressed systematically, for each subfield of plastic pollution research and it should be done now. Perfect methods and protocols might not exist in this field; however, consensus is needed on parameters such as the definition of size ranges, polymer types to focus on, analytical methods and indicator species, and from there recommend worldwide targeted policies, and protocols to monitor the effects of measures and regulations (e.g., Logemann et al., 2022 ). Various attempts at designing global protocols for plastic research have recently been published such as, among others Farmen et al. (2021) on microplastic monitoring in Arctic regions; Duncan et al. (2020) on the design of “bottle tags” to simulate plastic movement; The European Commission coastline microliter assessment protocol, and the OSPAR (Oslo and Paris Convention) marine litter assessment ( European Commission, 2020 ); Frias et al. (2018) for sediment analysis. Indicator species have been proposed such as Nephrops norvegicus ( Joyce et al., 2022 ) and tube dwelling polychaete species in the Oweniidae family ( Knutsen et al., 2020 ). For more detail, Multisanti et al. (2022) offer a comprehensive review of possible indicator species across taxa and advocate the use of a One Health approach to motivate the monitoring of sentinel species. Similarly, within the field of microplastic, various protocols are proposed and discussed. For sediment ( Bellasi et al., 2021 ) and water analysis ( Lee and Chae, 2021 ) a variety of analytical strategies are discussed, while Hermsen et al. (2018) and Tsangaris et al. (2021) present comprehensive protocols for biota analysis. These need to be reviewed by the scientific community and adopted, adapted or replaced. It is also important to involve NGOs and policymakers to create these guidelines, enabling research results suitable for policymakers. Establishing long-lasting international working groups should be the first step, as well as long-term financial support to these.

We need system change, not ecosystem change

The issue of plastic pollution has made media headlines for years but the system change and international regulations required to address this global issue are lagging behind. What can we as scientists hope to achieve in such circumstances? Riechers et al. (2021) used Donella Meadows’ leverage point framework ( Meadows, 1999 ) to show that only a very small proportion of journal articles addressing marine pollution dealt with it as a systemic socio-ecological problem. They encouraged researchers to investigate and to recommend changes in the deeper drivers of marine pollution such as proactive and preventive interventions to change values, goals and the intent of the system.

Many studies have documented local effects of plastic on vertebrate and invertebrate species, reviewed in, e.g., Lopez-Martinez (2020) ; Pirsaheb et al. (2020) ; Sönmez et al. (2022) . In addition, plastic has been hypothesised to impact the Earth as a system, by disrupting wider biogeochemical cycles in the ocean and soils ( Villarrubia-Gomez et al., 2018 ; Galgani and Loiselle, 2021 ; Rilling et al., 2021 ). For instance, Galgani and Loiselle (2021) have suggested that plastics in the ocean will ultimately change the balance of primary to secondary producers, the rate of sinking nutrients and the bioavailability of nutrients at deeper levels of the ocean. This combined with warmer temperatures and more acidic conditions, might ultimately have consequences on the carbon cycle and the ability of oceans to act as a sink for greenhouse gases. All in all, there is now backing to take plastic pollution seriously enough to call it a planetary boundary ( Villarrubia-Gomez et al., 2018 ; Arp et al., 2021 ). An update on the front of Planetary Boundaries for Novel Entities shows that we have now exceeded yet another boundary and that plastic is facilitating this process ( Persson et al., 2022 ). Moreover, the authors conclude that plastic production is closely linked to the planetary boundaries of biosphere integrity and that its production volume is a strong proxy for overall anthropogenic change ( Persson et al., 2022 ). Is it about time to use the precautionary principle to curb the problem?

When it comes to soils, there is evidence of plastic concentration in soils supporting this claim ( Zhang et al., 2020 ; Bastesen et al., 2021 ; Cyvin et al., 2021 ) suggesting that soil properties such as porosity, oxygen levels and pH might be changed by the presence of plastics and that, among others, plants ( Wang et al., 2022 ), invertebrates ( Ji et al., 2021 ) and microbial communities ( Huang et al., 2021 ) might be affected. In general, the terrestrial ecosystems are poorly investigated with regards to the concentrations and effects of plastic pollution ( Rilling et al., 2021 ).

Which systemic changes can we recommend as scientists to halt the input of plastic into the environment? Given the striking diversity of the plastic particles found and the challenges in recycling hybrid materials, would it be unthinkable to put a lid on plastic product diversification, misleadingly termed “innovation?”

Another systemic change that is underreported is the need to reduce our consumption of plastics. Indeed, we cannot assume that in the next years, we will see a surge of collection and recycling infrastructure with associated labour all over the world, which will completely rid us of the problem of “mismanagement.” Nor can we expect scientists or industries to invent a “technological fix” that will magically clean up the environment. On the contrary, as our consumption of single-use items increases worldwide, no recycling plant could cope, especially not on island nations or developing countries. Plastic is embedded in almost all aspects of our daily lives, and cutting plastic out seems an overwhelming task, given current trends in global use and production of plastic. The focus should be placed on limiting ourselves to essential single-use plastics (e.g., personal care products and healthcare, hygiene), use of long-lasting easily reusable and recyclable products where no realistic alternative exists. Active involvement of the industry as well as strong policy regulations are needed. Let us consider further the ubiquity of plastic in our lives and how it might impact human health.

Possible human health risks

Plastics are used increasingly in domestic products in the form of fibers, pellets or dust ( Henry et al., 2019 ; Steer and Thompson, 2020 ; Jenner et al., 2022 ). One of the most pressing questions about plastic pollution is related to possible human health effects. It is now established that plastic dust is present in the atmosphere, especially in cities, from decomposition of old plastic, presence in building materials and paints, vehicle tyres, etc. ( Ageel et al., 2022 ; Nematollahi et al., 2022 ). Indeed, Jenner et al. (2022) recently quantified microplastic particles in human lung tissue. Prata et al. (2020) , p. 7, on the other hand discuss possibilities for oxidative stress and inflammation, disruption of immune functions, neurotoxicity and neoplasia, and conclude that “more studies are needed to fully understand the risk of microplastics to human health.” But can we at the same time, already, encourage research into the deep drivers leading to possible health effects?

Ingestion of plastic by humans through drinking water and foods has also been widely documented (e.g., Danopoulos et al., 2020a ; Danopoulos et al., 2020b ). Although, it may be difficult to carry out research on human health effects of plastics due to ethical consideration, finding a control group ( Henry et al., 2019 ), and problems isolating plastics from other pollutants, if the pathways for health effects can be pinpointed in other species, as reviewed, for example, in Pirsaheb et al. (2020) , it does not defy scientific logic to assume that similar pathways exist with humans. One way of going around this issue is by quantifying exposure to plastics in our direct environments.

As a striking example, Ragusa et al. (2020) found the first evidence of microplastic in human placenta. Their study along with one from Sripada et al. (2022) , point out that foetus and infants are more than ever exposed to microplastic and associated pollutants from the placenta to breast milk to the very air they breathe, and dust they ingest. Moreover, foetuses and infants might not have a developed enough coping mechanism to exclude these pathogens from their metabolism, as adults ( Sripada et al., 2022 ). The effects are not well understood but it is reported that microplastic may create localised toxicity and trigger immune responses ( Sharifinia et al., 2021 ): Again—“it depends on … .”

When highlighting the ubiquity of plastics in industrial and household products, clear recommendations for how to reduce these substances should be developed. Henry et al. (2019) recommend including plastic fibre loss from household furniture in sustainability assessments. Woods et al. (2021) developed effect factors for the widely used Life Cycle Assessment tool and Maga et al. (2022) lay out the LCA methodology to include effect and exposure factors. Clear regulations should be issued for the private sector to not only document and limit the use of plastic polymers in their products but also to carry the burden of proof when it comes to safety.

Scientists are sounding alarm bells all around the globe with recommendations of incremental adjustments to the current system ( Riechers et al., 2021 ), while plastic inputs into nature and our bodies are reaching disturbing proportions. What happens after scientific findings are published can be conceptualised by observing other global environmental challenges as described in the next section. But it is time to use the precautionary principle and be bolder in our recommendations.

The role of scientists in policy-making

According to Watson-Wright (2005) , scientists and decision makers are ensnared in a “push” and “pull” dance, where scientists draw attention to a problem, policymakers then ask scientists for more information and recommendations and on it goes from there.

Marine pollution was mentioned already by the French author and explorer Jules Verne in 1870. Throughout the 1960s and 1970s, there were reports about marine plastic found in or entangled around birds, turtles, manatees, cetaceans and reports about plastic and micro plastic in general where published ( Ryan, 2015 ). Plastics have now been shown to be present in all the spheres we operate in, from the biosphere, to the atmosphere, the cryosphere and hydrosphere ( Kim et al., 2021 ; MacLeod et al., 2021 ). Many governments and international organisations then came back to the scientific community to ask for more research ( Figure 1 ). One of the latest, and also widely misinterpreted (in the media) calls for research was by the World Health Organization on the effects of microplastic on human health from drinking water ( WHO, 2021 ).

FIGURE 1 . Simplified and conceptual drawing of the push-and-pull dynamic between researchers, policymakers and the ultimate development of international agreements. The x -axis represents time, while the green line shows how the pollutant increases in production and thereby also the pollution rises. The figure could describe the greenhouse gas situation over the last decades, and it could also describe the case of plastic pollution, where 2022 is different places on the x -axis dependent on the pollutant. The content in the international agreements, and thereby the national regulations and initiatives, and ultimately systemic change or not would define whether conceptual scenario A, B or C would be possible. Figure: Cyvin and Hellevik, 2023.

Scientists are then asked to make policy recommendations, and this is where we as researchers could make an impact. However, most articles conclude that we need more research or better management and clean-up, i.e., low-impact measures targeting the tail-end rather than the source of the problem ( Riechers et al., 2021 ). Scientists should express themselves clearly and confidently when they find indications of severe effects of plastics, they should share their extrapolation exercise from small-scale impacts to ecosystem or even planetary level, and they should demand clear systemic changes when their results demand them. Some researchers might find this as out of their domain, but it can be done without compromising our research ethics boundaries if our recommendations are research based, and driven by evidence, not feelings. Maybe it is also time to tailor national and European research grants towards the systemic level, and its implementation into society? More research is of course needed, but that is, based on current knowledge about global severity, an absolute given.

In Figure 1 , we broadly conceptualise the dynamic of push-and-pull between researchers, policymakers, time elapsing during these processes, meanwhile the pollution levels rise. We could place different pollutants or environmental issues into the conceptual model. The current possibility of reaching an early decline in the level of pollution (scenario C), might be overdue for plastic as a contaminant, but maybe we can reach scenario B instead of A if we manage to work together as an international community of researchers, NGOs, policymakers, and industries.

The pattern we are currently witnessing seems to lead towards scenario A in Figure 1 . Decision makers call for more science, better information, better infrastructure to deal with the waste, discussions about which countries are responsible for the most plastic pollution and where it occurs. UNEP have, to frame it simply, achieved an international agreement about creating an international agreement ( UNEP, 2022 ). The latter was demanded by Borelle et al. (2017) and before that by Rochman et al. (2013) . But so far, there is limited content to be read in this agreement. It is, indeed, a paper with great possibilities, but so far, the paper is quite empty and without specific text or value.

Historic success can be repeated

Plastic is not the one and only environmental threat, but it is one very visible result of a long-term systemic failure. The Montreal Protocol is a great success story showing the power of collective action, which resulted in banning CFCs and halting the depletion of our ozone Layer.

Our concluding statement is that the research front now presents plastic as globally ubiquitous in nature and in humans’ direct environment. Effects have been shown locally, and hypothesised plausibly on global biogeochemical cycles. This, combined with predictions of ever-increasing production and pollution is disturbing and should make us question the goals and intent of our economic/political system. Marine plastic pollution should, in terms of severity and policy priority be treated as the ozone layer depletion was. There are huge differences between these two environmental issues, but we can be inspired by the Montreal protocol from 1987. Let us together tackle and overcome ( Figure 1 leading to scenario C) the issue as a global community of researchers, policymakers, industry, and civil society; this is also possible now. As researchers, journal editors and reviewers, we must be bold in our communication of results and policy recommendations while maintaining our academic integrity. Meanwhile, policymakers and civil society must take our findings on board and prioritise issues threatening nature and societies. We cannot play out multiple grand experiments with our health and nature ( Andrady and Neal, 2009 , Wright and Kelly, 2017 ).

Data availability statement

The raw data supporting the conclusion of this article will be made available by the authors, without undue reservation.

Author contributions

JBC and CH have shared all aspects of the publication process, from sketching to conceptualization, data analysis and writing of final manuscript as well as editing. All authors contributed to the article and approved the submitted version.

Both authors received funding from the Norwegian University of Science and Technology to carry out this research as part of their PhD grant from NTNU (JBC from NTNU Sustainability). The publication cost was covered by the University publication agreements.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Ageel, H. K., Harrad, S., and Abdallah, M. A.-E. (2022). Occurrence, human exposure, and risk of microplastics in the indoor environment. Environ. Sci. Process. Impacts 24 (1), 17–31. doi:10.1039/D1EM00301A

PubMed Abstract | CrossRef Full Text | Google Scholar

Andrady, A. L., and Neal, M. A. (2009). Applications and societal benefits of plastics. Philosophical Trans. R. Soc. B Biol. Sci. 364 (1526), 1977–1984. doi:10.1098/rstb.2008.0304

CrossRef Full Text | Google Scholar

Arp, H. P. H., Kühnel, D., Rummel, C., MacLeod, M., Potthoff, A., Reichelt, S., et al. (2021). Weathering plastics as a planetary boundary threat: Exposure, fate, and hazards. Environ. Sci. Technol. 55 (11), 7246–7255. doi:10.1021/acs.est.1c01512

Bastesen, E., Haave, M., Andersen, G. L., Velle, G., Bødtker, G., and Krafft, C. G. (2021). Rapid landscape changes in plastic bays along the Norwegian coastline. Front. Mar. Sci. 8, 579913. doi:10.3389/fmars.2021.579913

Bellasi, A., Binda, G., Pozzi, A., Boldrocchi, G., and Bettinetti, R. (2021). The extraction of microplastics from sediments: An overview of existing methods and the proposal of a new and green alternative. Chemosphere 278, 130357. doi:10.1016/j.chemosphere.2021.130357

Bonanno, G., and Orlando-Bonaca, M. (2020). Marine plastics: What risks and policies exist for seagrass ecosystems in the Plasticene? Mar. Pollut. Bull. 158, 111425. doi:10.1016/j.marpolbul.2020.111425

Borelle, S. B., Rochman, C. M., Liboiron, M., Bond, A. L., Lusher, A., Bradshaw, H., et al. (2017). Why we need an international agreement on marine plastic pollution. Proc. Natl. Acad. Sci. 114 (38), 9994–9997. doi:10.1073/pnas.1714450114

Chassignet, E. P., Xu, X., and Zavala-Romero, O. (2021). Tracking marine litter with a global ocean model: Where does it go? Where does it come from? Front. Mar. Sci. 8, 667591. doi:10.3389/fmars.2021.667591

Cyvin, J. B., Ervik, H., Kveberg, A. A., and Hellevik, C. (2021). Macroplastic in soil and peat. A case study from the remote islands of Mausund and Froan landscape conservation area, Norway; implications for coastal cleanups and biodiversity. Sci. Total Environ. 787, 147547. doi:10.1016/j.scitotenv.2021.147547

Danopoulos, E., Jenner, L. C., Twiddy, M., and Rotchell, J. M. (2020a). Microplastic contamination of seafood intended for human consumption: A systematic review and meta-analysis. Environ. Health Perspect. 128 (12), 126002. doi:10.1289/EHP7171

Danopoulos, E., Twiddy, M., and Rotchell, J. M. (2020b). Microplastic contamination of drinking water: A systematic review. PLOS ONE 15 (7), e0236838. doi:10.1371/journal.pone.0236838

Duncan, E. M., Davies, A., Brooks, A., Chowdhury, G. W., Godley, B. J., Jambeck, J., et al. (2020). Message in a bottle: Open source technology to track the movement of plastic pollution. PLOS ONE 15 (12), e0242459. doi:10.1371/journal.pone.0242459

European Commission. Joint Research Centre, (2020). A European threshold value and assessment method for macro litter on the coastlines . Brussels, Belgium: European Commission .

Google Scholar

Farmen, E., Provencher, J., Aliani, S., Baak, J., Bergmann, M., Booth, A. M., et al. (2021). Litter and microplastics monitoring guidelines arctic monitoring & assessment programme . https://www.amap.no/documents/download/6761/inline . doi:10.13140/RG.2.2.34524.72324

Frias, J. P. G. L., Pagter, E., Nash, R., O’Connor, I., Carretero, O., Filgueiras, A., et al. (2018). Standardised protocol for monitoring microplastics in sediments . P4 Deliverable D4.2 (Galway City, Mayo, Connemara: GMIT ). doi:10.13140/RG.2.2.36256.89601/1

Galgani, L., and Loiselle, S. A. (2021). Plastic pollution impacts on marine carbon biogeochemistry. Environ. Pollut. 268, 115598. doi:10.1016/j.envpol.2020.115598

Henry, B., Laitala, K., and Klepp, I. G. (2019). Microfibres from apparel and home textiles: Prospects for including microplastics in environmental sustainability assessment. Sci. Total Environ. 652, 483–494. doi:10.1016/j.scitotenv.2018.10.166

Hermsen, E., Mintenig, S. M., Besseling, E., and Koelmans, A. A. (2018). Quality criteria for the analysis of microplastic in biota samples: A critical review. Environ. Sci. Technol. 52 (18), 10230–10240. doi:10.1021/acs.est.8b01611

Huang, D., Xu, Y., Lei, F., Yu, X., Ouyang, Z., Chen, Y., et al. (2021). Degradation of polyethylene plastic in soil and effects on microbial community composition. J. Hazard. Mater. 416, 126173. doi:10.1016/j.jhazmat.2021.126173

Huserbråten, M. B. O., Hattermann, T., Broms, C., and Albretsen, J. (2022). Trans-polar drift-pathways of riverine European microplastic. Sci. Rep. 12 (1), 3016. doi:10.1038/s41598-022-07080-z

Jacquin, J., Cheng, J., Odobel, C., Pandin, C., Conan, P., Pujo-Pay, M., et al. (2019). Microbial ecotoxicology of marine plastic debris: A review on colonization and biodegradation by the “plastisphere”. Front. Microbiol. 10, 865. doi:10.3389/fmicb.2019.00865

Jenner, L. C., Rotchell, J. M., Bennett, R. T., Cowen, M., Tentzeris, V., and Sadofsky, L. R. (2022). Detection of microplastics in human lung tissue using μFTIR spectroscopy. Sci. Total Environ. 831, 154907. doi:10.1016/j.scitotenv.2022.154907

Ji, Z., Huang, Y., Feng, Y., Johansen, A., Xue, J., Tremblay, L. A., et al. (2021). Effects of pristine microplastics and nanoplastics on soil invertebrates: A systematic review and meta-analysis of available data. Sci. Total Environ. 788, 147784. doi:10.1016/j.scitotenv.2021.147784

Joyce, H., Frias, J., Kavanagh, F., Lynch, R., Pagter, E., White, J., et al. (2022). Plastics, prawns, and patterns: Microplastic loadings in Nephrops norvegicus and surrounding habitat in the North East Atlantic. Sci. Total Environ. 826, 154036. doi:10.1016/j.scitotenv.2022.154036

Khalid, N., Aqeel, M., Noman, A., Hashem, M., Mostafa, Y. S., Alhaithloul, H. A. S., et al. (2021). Linking effects of microplastics to ecological impacts in marine environments. Chemosphere 264, 128541. doi:10.1016/j.chemosphere.2020.128541

Kim, S.-K., Lee, H.-J., Kim, J.-S., Kang, S.-H., Yang, E.-J., Cho, K.-H., et al. (2021). Importance of seasonal sea ice in the Western Arctic ocean to the Arctic and global microplastic budgets. J. Hazard. Mater. 418, 125971. doi:10.1016/j.jhazmat.2021.125971

Kirstein, I. V., Kirmizi, S., Wichels, A., Garin-Fernandez, A., Erler, R., Löder, M., et al. (2016). Dangerous hitchhikers? Evidence for potentially pathogenic Vibrio spp. on microplastic particles. Mar. Environ. Res. 120, 1–8. doi:10.1016/j.marenvres.2016.07.004

Knutsen, H., Cyvin, J. B., Totland, C., Lilleeng, Ø., Wade, E. J., Castro, V., et al. (2020). Microplastic accumulation by tube-dwelling, suspension feeding polychaetes from the sediment surface: A case study from the Norwegian continental shelf. Mar. Environ. Res. 161, 105073. doi:10.1016/j.marenvres.2020.105073

Lee, J., and Chae, K.-J. (2021). A systematic protocol of microplastics analysis from their identification to quantification in water environment: A comprehensive review. J. Hazard. Mater. 403, 124049. doi:10.1016/j.jhazmat.2020.124049

Logemann, A., Reininghaus, M., Schmidt, M., Ebeling, A., Zimmermann, T., Wolschke, H., et al. (2022). Assessing the chemical anthropocene – development of the legacy pollution fingerprint in the North Sea during the last century. Environ. Pollut. 302, 119040. doi:10.1016/j.envpol.2022.119040

López-Martínez, S., Morales-Caselles, C., Kadar, J., and Rivas, M. L. (2020). Overview of global status of plastic presence in marine vertebrates. Glob. Change Biol. 27 (4), 728–737. doi:10.1111/gcb.15416

MacLeod, M., Arp, H. P. H., Tekman, M. B., and Jahnke, A. (2021). The global threat from plastic pollution. Science 373 (6550), 61–65. doi:10.1126/science.abg5433

Maga, D., Galafton, C., Blömer, J., Thonemann, N., Özdamar, A., and Bertling, J. (2022). Methodology to address potential impacts of plastic emissions in life cycle assessment. Int. J. Life Cycle Assess. 27 (3), 469–491. doi:10.1007/s11367-022-02040-1

Meadows, D. (1999). Leverage points: Places to intervene in a system . Hartland, WI: The Sustainability Institute .

Multisanti, C. R., Merola, C., Perugini, M., Aliko, V., and Faggio, C. (2022). Sentinel species selection for monitoring microplastic pollution: A review on one health approach. Ecol. Indic. 145, 109587. doi:10.1016/j.ecolind.2022.109587

Nematollahi, M. J., Zarei, F., Keshavarzi, B., Zarei, M., Moore, F., Busquets, R., et al. (2022). Microplastic occurrence in settled indoor dust in schools. Sci. Total Environ. 807, 150984. doi:10.1016/j.scitotenv.2021.150984

Persson, L., Carney Almroth, B. M., Collins, C. D., Cornell, S., de Wit, C. A., Diamond, M. L., et al. (2022). Outside the safe operating space of the planetary boundary for novel entities. Environ. Sci. Technol. 56 (3), 1510–1521. doi:10.1021/acs.est.1c04158

Pirsaheb, M., Hossini, H., and Makhdoumi, P. (2020). Review of microplastic occurrence and toxicological effects in marine environment: Experimental evidence of inflammation. Process Saf. Environ. Prot. 142, 1–14. doi:10.1016/j.psep.2020.05.050

Prata, J. C., da Costa, J. P., Lopes, I., Duarte, A. C., and Rocha-Santos, T. (2020). Environmental exposure to microplastics: An overview on possible human health effects. Sci. Total Environ. 702, 134455. doi:10.1016/j.scitotenv.2019.134455

Ragusa, A., Svelato, A., Santacroce, C., Catalano, P., Notarstefano, V., Carnevali, O., et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environ. Int. 146, 106274. doi:10.1016/j.envint.2020.106274

Riechers, M., Brunner, B. P., Dajka, J.-C., Dușe, I. A., Lübker, H. M., Manlosa, A. O., et al. (2021). Leverage points for addressing marine and coastal pollution: A review. Mar. Pollut. Bull. 167, 112263. doi:10.1016/j.marpolbul.2021.112263

Rillig, M. C., Leifheit, E., and Lehmann, J. (2021). Microplastic effects on carbon cycling processes in soils. PLOS Biol. 19 (3), e3001130. doi:10.1371/journal.pbio.3001130

Rochman, C. M., Browne, M. A., Halpern, B. S., Hentschel, B. T., Hoh, E., Karapanagioti, H. K., et al. (2013). Classify plastic waste as hazardous. Nature 494 (7436), 169–171. doi:10.1038/494169a

Ryan, P. G. (2015). “A brief history of marine litter research,” in Marine anthropogenic litter . Editor I. M. Bergmann, L. Gutow, and M. Klages ( Springer International Publishing ), 1–25. doi:10.1007/978-3-319-16510-3_1

Sharifinia, M., Bahmanbeigloo, Z. A., Keshavarzifard, M., Khanjani, M. H., and Lyons, B. P. (2020). Microplastic pollution as a grand challenge in marine research: A closer look at their adverse impacts on the immune and reproductive systems. Ecotoxicol. Environ. Saf. 204, 111109. doi:10.1016/j.ecoenv.2020.111109

Sönmez, V. Z., Akarsu, C., and Sivri, N. (2022). “The ecotoxicological effects of microplastics on trophic levels of aquatic ecosystems,” in Microplastic pollution . Editor I. M. Z. Hashmi ( Springer International Publishing ), 389–428. doi:10.1007/978-3-030-89220-3_18

Sripada, K., Wierzbicka, A., Abass, K., Grimalt, J. O., Erbe, A., Röllin, H. B., et al. (2022). A children’s health perspective on nano- and microplastics. Environ. Health Perspect. 130 (1), 015001. doi:10.1289/EHP9086

Steer, M., Thompson, R. C., Streit-Bianchi, I. M., Cimadevila, M., and Trettnak, W. (2020). “Plastics and microplastics: Impacts in the marine environment,” in Mare plasticum—the plastic sea (Berlin, Germany: Springer International Publishing ). doi:10.1007/978-3-030-38945-1_3

Strand, K. O., Huserbråten, M., Dagestad, K.-F., Mauritzen, C., Grøsvik, B. E., Nogueira, L. A., et al. (2021). Potential sources of marine plastic from survey beaches in the Arctic and Northeast Atlantic. Sci. Total Environ. 790, 148009. doi:10.1016/j.scitotenv.2021.148009

Tsangaris, C., Panti, C., Compa, M., Pedà, C., Digka, N., Baini, M., et al. (2021). Interlaboratory comparison of microplastic extraction methods from marine biota tissues: A harmonization exercise of the plastic busters MPAs project. Mar. Pollut. Bull. 164, 111992. doi:10.1016/j.marpolbul.2021.111992

United Nations Environment Assembly Programme (Unep), (2022). End plastic pollution: Towards an international legally binding instrument (EA.5/Res.14). https://wedocs.unep.org/xmlui/bitstream/handle/20.500.11822/39764/END%20PLASTIC%20POLLUTION%20-%20TOWARDS%20AN%20INTERNATIONAL%20LEGALLY%20BINDING%20INSTRUMENT%20-%20English.pdf?sequence=1&isAllowed=y .

Villarrubia-Gómez, P., Cornell, S. E., and Fabres, J. (2018). Marine plastic pollution as a planetary boundary threat – the drifting piece in the sustainability puzzle. Mar. Policy 96, 213–220. doi:10.1016/j.marpol.2017.11.035

Watson-Wright, W. M. (2005). “Policy and science: different roles in the pursuit of solutions to common problems,” in Politics and socio-economics of ecosystem-based management of marine resources . Editor H. I. Browman, and K. I. Stergiou ( Marine Ecology Progress Series ) 300, 291–296.

Wagner, M., and Bank, I. M. S. (2022). “Solutions to plastic pollution: A conceptual framework to tackle a wicked problem,” in Microplastic in the environment: Pattern and process (Berlin, Germany: Springer International Publishing ). doi:10.1007/978-3-030-78627-4_11

Wang, F., Feng, X., Liu, Y., Adams, C. A., Sun, Y., and Zhang, S. (2022). Micro(nano)plastics and terrestrial plants: Up-to-date knowledge on uptake, translocation, and phytotoxicity. Resour. Conservation Recycl. 185, 106503. doi:10.1016/j.resconrec.2022.106503

World Health Organisation (WHO), (2021). Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health . Geneva: World Health Organization . Available at: https://www.who.int/publications/i/item/9789240054608

Woods, J. S., Verones, F., Jolliet, O., Vázquez-Rowe, I., and Boulay, A.-M. (2021). A framework for the assessment of marine litter impacts in life cycle impact assessment. Ecol. Indic. 129, 107918. doi:10.1016/j.ecolind.2021.107918

Wright, S. L., and Kelly, F. J. (2017). Plastic and human health: A micro issue? Environ. Sci. Technol. 51 (12), 6634–6647. doi:10.1021/acs.est.7b00423

Zhang, B., Yang, X., Chen, L., Chao, J., Teng, J., and Wang, Q. (2020). Microplastics in soils: A review of possible sources, analytical methods and ecological impacts. J. Chem. Technol. Biotechnol. 95 (8), 2052–2068. doi:10.1002/jctb.6334

Keywords: plastic pollution, marine plastic, terrestrial ecosystems, wicked problem, biogeochemical cycles, planetary boundaries, human health

Citation: Hellevik CC and Cyvin JB (2023) Plastic pollution: about time to unify research methods and demand systemic changes. Front. Environ. Sci. 11:1232974. doi: 10.3389/fenvs.2023.1232974

Received: 01 June 2023; Accepted: 04 July 2023; Published: 17 July 2023.

Reviewed by:

Copyright © 2023 Hellevik and Cyvin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Jakob Bonnevie Cyvin, [email protected] ; Christina Carrozzo Hellevik, [email protected]

† These authors have contributed equally to this work and share first authorship

April 3, 2024

11 min read

Earth Is Drowning in Plastic. Can an International Treaty Help?

A marine scientist discusses the problem of plastic pollution and her hopes for an international treaty to tackle it

By Nicola Jones & Knowable Magazine

The problem of plastic pollution grows greater with each passing year.

Larina Marina/Getty Images

Our world is increasingly plastic. Back in the 1950s, humanity produced just 5 million metric tons of plastic per year; today it’s 400 million metric tons. Since plastic can take hundreds or thousands of years to biodegrade, pretty much all of it is still around, except for the roughly 20 percent that’s been burned. By some estimates, there are now eight gigatons of accumulated plastic on Earth — twice as much as the weight of all animal life.

Much of this plastic is still in use, in products like cars and homes, but a lot is junk; 40 percent of plastic production goes toward packaging that’s typically tossed after being used once. Some of our plastic waste is recycled, responsibly incinerated or properly landfilled, but tens of millions of tons are mismanaged annually — burned in open pits or left to pollute the environment. Plastic pollution has been found at the poles and the bottom of the ocean , in our clouds and soils , in human blood and mothers’ milk . If things keep going as they are, it is predicted that annual rates of plastic flowing into the sea will triple from 2016 to 2040.

The impacts are manifold. Debris can choke and tangle wildlife; even zooplankton can fill up on microplastics instead of food, altering how much oxygen is in the ocean. And some of the chemicals used in plastics — including additives that make plastics flexible or fire-resistant — can leach out into water, soil or our bodies. Some of these are carcinogenic or endocrine disruptors, capable of interfering with development or reproduction. The net impacts of our lifelong exposure to this chemical soup are hard to tease out, but one recent study concluded that it cost the United States $249 billion in extra health care in 2018.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Delegates are working now on the world’s first plastic pollution treaty , which is due to be completed by the end of this year. That treaty might cap plastic production, phase out problem chemicals and regulate how waste is managed — but how ambitious this treaty will be is yet to be seen. (See box.)

Imogen Napper, a marine science postdoc at the University of Plymouth in the United Kingdom who specializes in plastic pollution, is one of many scientists whose research is informing the treaty process. Her detective work has documented plastic pollution in surprising places and pointed to solutions that have made their way into government regulations around the world. Knowable Magazine spoke with her about the plastic problem and what we can all do about it. This conversation has been edited for length and clarity.

Why did you decide to focus on plastic pollution as a researcher?

I was lucky to grow up in a small seaside town in the southwest of the UK. I don’t remember any discussion about plastic pollution or beach cleanups when I was younger. But now, going back home, plastic pollution is one of the most obvious environmental challenges that we have, because it’s so visible.

I’m hoping that plastic pollution can be used as a gateway issue to other environmental concerns. Climate change , I’d argue, is a far bigger beast than plastic pollution. But for plastic pollution, we’ve got all the tools that we need — we’ve got potential solutions, and discussion happening now through the plastics treaty. We have that burning fire of desire to make a change. We can fix it.

You and many other researchers spend a lot of time documenting where plastic is in the wild, and how it gets there. Why is this so hard?

When it comes to microscopic pieces in, say, a soil or water sample, it takes a lot of grunt work. I have spent a lot of time looking under the microscope trying to identify, just from the look of it, whether something is cellulosic — coming from plants, like cotton — or plastic. You get a good eye for it. But it can be really tricky.

Nor is it easy to document the accumulation and distribution of bigger, macro-sized chunks of plastic. There are so many sources, leakage points and places where plastic is building up. In one of our studies, led by Emily Duncan at the University of Exeter, we put GPS tags in plastic bottles and tracked them thousands of kilometers down the Ganges River. That sort of work helps to improve scientific models.

The commonly used estimate is that about 8 million metric tons of macroplastic enter the ocean each year. We know a lot less about the land. Technology is getting far better, with remote sensing, drones and satellite imagery . That will be very useful in the next few years to help us accurately identify how much plastic is going into the environment.

A lot of plastic litter is single-use products that have been tossed aside: In the UK, one survey showed that more than half of plastic litter was beverage-related, including cups, lids and straws. But some sources are more surprising, like tiny pieces of plastic thrown up by tire wear on highways.

That was also surprising to me. It’s so obvious — it’s right in front of you — but often we just don’t consider it. Research has only really focused on tire wear in the last few years, but it’s predicted to be one of the biggest single sources of microplastics — it has been estimated to make up five to 10 percent of the plastic entering the ocean.

In our lab, we have done a lot of research looking at clothing. I’d say about 60 percent of our wardrobe contains plastic, like polyester, acrylic or a natural-synthetic blend. A big part of my PhD research was centered around building a washing machine lab, and I tested for the first time different fabrics to see how many fibers would come off in a typical wash .

We found that for acrylic it was the most, at 700,000 fibers per wash. For polyester-cotton blend, it was a lot less, around 130,000 fibers. This started discussions about how we might make clothes differently or change our washing machines. In France, by 2025 all new washing machines will have to come with a filter, which is exciting. It’ll be really interesting to see how that develops. Ideally, the filter should be reusable, so we’re not just making more potential rubbish. There are a lot of different options ; independent testing will be important.

Where does all this plastic wind up?

You could argue that plastic really is everywhere. We did some research that found plastic fibers just below the summit of Mount Everest . In some regions, plastic microfibers can go down the drain into the sewage treatment plants; the collected solids, called sewage sludge, is then treated and then often applied on agricultural land as fertilizer. There’s evidence that the chemicals in those plastics can then be absorbed into plants .

There are some surprising ecological effects, too. I have read that some plastic pieces, because of their dark colors, absorb heat, which means they’re contributing to melting snow and ice .

Yes. Plastic can also increase sand temperature, and this has been found in turtle nesting sites . And turtle sex is dependent on the temperature of the sand. So we might end up with a lot more female turtles.

What’s the best thing to do with plastic at the end of its life?

Landfill isn’t great, but it does contain and control waste when done right. Incineration has pros and cons; it gets rid of the plastic and can be used to make energy. A lot of small island developing states may use incineration because they haven’t got the space for landfill, but then it’s often open burning, which is not good for the planet or your health.

People often think that recycling is a golden solution. But recycling is not fully circular — the recycled plastic is often made into a polymer of worsening quality. At some point, it will not be recyclable. Recycling can also generate problematic microplastics. And if there isn’t a market for the recycled material , it can end up in landfill.

None of this gets rid of the core issue. It’s just delaying it. I’m a big believer of tackling the problem at its source. My supervisor, Richard Thompson, says plastic pollution is like an overfilling bath. We’re very good at mopping up the floor, but the bath keeps overflowing. What we need to do is turn off the tap.

Are there good alternatives to conventional plastic, like biodegradable or compostable plastics, or bioplastics that are made from plants rather than from fossil fuels?

We did some research on this. We did a study looking at biodegradable carrier bags : We buried them in the soil, we submerged them in the ocean, and we left them hanging outside for three years. The ones outside completely fragmented into tiny bits — the plastic didn’t disappear, it just got smaller. The ones in the soil and in the ocean could still hold a full bag of shopping.

Biodegradable plastics that are marketed today need to go into a really specific waste management facility with high moisture, high heat, maybe a certain pH, to disappear.

Many bioplastics used today — such as bio-polyethylene — are chemically the same as other plastics, just made from a different source. They’re made from plant carbon instead of from fossil fuel carbon, but they may behave exactly like all other plastic. If they’re still single use, is that any better?

There’s a lot of work going into alternative products , but we need to be careful that they’re actually better for our health and the environment.

How is the plastics treaty (see box) coming along?

It’s going to take a lot of discussion, and I will be delighted if it happens this year, but realistically, I think it is going to take a little bit more time. It is difficult to get nations to agree to firm action, because a lot of it comes down to money — both the money to be made from manufacturing plastic, and the money it costs to deal with waste.

This is an amazing opportunity that we have, where globally we can have a unified decision on how to protect our planet. The treaty needs to be ambitious, it needs to be specific, and it needs to be binding.

Is it reasonable to think that some plastics might be banned?

Legislation has already banned some plastics and additives in some countries or regions. Our lab quantified microbeads in beauty products : We found that 3 million microbeads could be in a bottle of facial scrub. So there can be thousands in a squirt on your hand. We took this research, we published it, and then one day I came in to work and I had so many emails in my inbox from journalists. It was making quite a stir. And there were campaigns like “ Beat the microbead ,” because consumers didn’t want to wash their faces with plastic.

So the consumers started to boycott the products, then industry voluntarily removed microbeads and showcased that information in their own marketing. And then governments around the world started to ban microbeads in facial scrubs.

Research is all about providing information. And then, with that information, people can take it forward and make a change. I feel very privileged to be in a position that I can be part of that.

If you were in charge, would you ban specific plastics or chemicals?

I’d flip the question on its head and ask: What would I keep? We don’t need all the plastic we make. And instead of using a big chemical cocktail of additives that we don’t know anything about, let’s just have a list of the chemicals that we can use.

When I started my PhD, I wrongly thought that plastic was evil. Plastics are incredibly useful and can solve other environmental and health problems. Plastic can keep our food fresh, and food waste is a huge problem. During the pandemic, it helped to keep people safe. It is lightweight, so products need less energy for transport.

But let’s think, right from when we’re designing it, how can we make sure it’s sustainable? Often, we’re not thinking about that right at the beginning, we’re thinking about it far down at the end of its life.

Treaty timeline

In 2022, 175 nations at the United Nations Environment Assembly agreed to draft a legally binding treaty against plastic pollution by 2024. That work is now underway, but progress has been slow, leaving observers wondering if it will be completed as planned at the meeting in Busan, South Korea, this December — and, if so, how ambitious it will be.

In 2023, delegates released an updated, 70-page pre- draft outlining issues to be tackled, along with a handful of options for how to address them. The issues span the full lifecycle of plastics — from their creation, including the greenhouse gases emitted during their production, through to the uses of plastics (including as single-use products and microbeads), to recycling and waste management. Topics such as tax schemes and pots of money for capacity-building in poorer nations get their share of coverage too.

The options for each issue range from hard to soft: Even the options for the stated objective of the treaty, for example, span from “to end plastic pollution” to the much gentler “to protect human health and the environment from plastic pollution.”

Many observers at the treaty’s third meeting , in Nairobi in November 2023, said that agreement on firm solutions seemed far away, with delegates from some fossil fuel-rich nations, including Saudi Arabia, pushing against hard production caps. Analysts have noted that as the planet cracks down on burning fossil fuels for energy, the oil industry has increasingly focused on plastic production as a profitable market.

On the other hand, a group of nations led by Norway and Rwanda — called the “ high ambition coalition ” — is pressing for strong action. “It’s a bit of a roller coaster,” says marine biologist Richard Thompson, Imogen Napper’s PhD supervisor at the University of Plymouth; he attended the treaty meeting as one of the coordinators of the independent Scientists’ Coalition for an Effective Plastics Treaty . “There’s great support and traction in one direction — and half an hour later, things seem to turn.”

One scientific model shows that it will take an extremely ambitious bundle of policies to drive mismanaged waste down. By this model, for example, cutting mismanaged plastic waste by 85 percent by 2050 would require implementing a 90 percent reduction in single-use packaging, a cap on primary plastic production at 2025 levels, and a mandate that at least 40 percent of plastics be recycled and that more than 40 percent of new products be made from recycled content — along with heavy taxes and more than $200 billion of investments in global waste infrastructure.

Scientists are also thinking hard about the treaty’s proposed list of polymers and chemicals of concern , which could be used to guide bans by specific dates, or just to encourage regulation. Such a list could include, for example, polyvinyl chloride (PVC) and polystyrene — often called “the toxic two” by environmental groups — alongside additives including phthalates (which are often used to make PVC more flexible and some of which are endocrine disrupters).

Many analysts and concerned observers would like to see the plastic treaty modeled after the Montreal Protocol on Substances That Deplete the Ozone Layer, which in 1986 famously phased out specific chemicals like chlorofluorocarbons with hard, time-targeted commitments. But it might, alternatively, be modeled more like the Paris Agreement on Climate Change, which allows nations to determine their own targets for action. That might be easier to agree upon, but less ambitious.

“It’s difficult to get all these nations to agree on all the nuts and bolts,” says Thompson. It remains to be seen how things will pan out at the next meeting , scheduled for Ottawa, Canada, this April.

Thompson remains hopeful for a big change in how society uses plastic. “It’s so cheap we can use it for a few seconds before throwing it away. That’s the problem,” he says. But, he adds, “a problem we can solve.”

— Nicola Jones

This article originally appeared in Knowable Magazine , an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter .

Plastics in the Aquatic Environment - Part II pp 13–38 Cite as

Human Perceptions and Behaviour Determine Aquatic Plastic Pollution

• Sabine Pahl 17 , 18 ,
• Isabel Richter 17 &
• Kayleigh Wyles 17 , 19  
• First Online: 26 October 2020

1344 Accesses

8 Citations

4 Altmetric

Part of the book series: The Handbook of Environmental Chemistry ((HEC,volume 112))

Aquatic plastic pollution is entirely due to humans. Throughout the whole life cycle of plastic, from production via consumption to disposal, it is human decisions and behaviour that ultimately lead to plastic ending up in aquatic environments. Every sector, every individual plays a role in the fate of plastic waste. For example, designers and producers make decisions about materials, appearance and functionality; consumers make purchasing decisions and dispose of items after use; policy makers decide on regulation and legal frameworks. These processes can be documented and explained using theories and methods from the social and behavioural sciences. More importantly, these insights can guide social change processes systematically and help develop and evaluate effective communication and behaviour change interventions. This chapter will summarise recent work on the human dimension in aquatic plastic pollution. Our focus will be on relevant literature from social and environmental psychology on risk perception, risk communication and behaviour change. We will draw on interdisciplinary and international work to highlight challenges to such integrative research and misunderstandings between disciplines. We will include research on macro- and microplastics and a range of stakeholders such as fishermen, the general public and young people. This will be complemented by a selective review of research on littering, media coverage and international initiatives. Finally, we will summarise remaining challenges and outline gaps in research.

• Social norms

This is a preview of subscription content, log in via an institution .

Buying options

• Available as PDF
• Read on any device
• Instant download
• Own it forever
• Available as EPUB and PDF
• Compact, lightweight edition
• Dispatched in 3 to 5 business days
• Free shipping worldwide - see info
• Durable hardcover edition

Tax calculation will be finalised at checkout

Purchases are for personal use only

Pahl S, Wyles KJ, Thompson RC (2017) Channelling passion for the ocean towards plastic pollution. Nat Hum Behav 1(10):697–699

Article   Google Scholar  

Jambeck JR et al (2015) Plastic waste inputs from land into the ocean. Science 347(6223):768–771

Article   CAS   Google Scholar  

Beaumont NJ et al (2019) Global ecological, social and economic impacts of marine plastic. Mar Pollut Bull 142:189–195

Law KL (2017) Plastics in the marine environment. Annu Rev Mar Sci 9:205–229

Galgani L et al (2019) Impacts of marine litter. Front Mar Sci 6:208

SAPEA, Science Advice for Policy by European Academies (2019) A scientific perspective on microplastics in nature and society. SAPEA, Berlin. https://doi.org/10.26356/microplastics . https://www.sapea.info/microplastics-launch/

Book   Google Scholar  

World Health Organization (2019) Microplastics in drinking-water. Geneva. License: CC

Google Scholar  

GESAMP (2020) In: Kershaw PJ, Carney Almroth B, Villarrubia-Gómez P, Koelmans AA, Gouin T (eds) Proceedings of the GESAMP international workshop on assessing the risks associated with plastics and microplastics in the marine environment. (IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/ UNEP/UNDP/ISA Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). Reports to GESAMP No. 103, 68 pp. http://www.gesamp.org/publications/gesamp-international-workshop-on-assessing-the-risks-associated-with-plastics-and-microplastics-in-the-marine-environment

European Commission. A European strategy for plastics in a circular economy

Sunstein CR (2019) How change happens. MIT Press

Independent (2020). https://www.independent.co.uk/news/world/americas/new-york-plastic-bag-ban-twitter-blacklash-single-use-plastics-a9371061.html

Telegraph (2018). https://www.telegraph.co.uk/news/2018/08/01/top-australian-supermarket-backs-plastic-bag-ban-critics-blame/

Alpizar F et al (2020) A framework for selecting and designing policies to reduce marine plastic pollution in developing countries. Environ Sci Pol 109:25–35

Gupta K (2011) Consumer responses to incentives to reduce plastic bag use: evidence from a field experiment in urban India, Nepal: South Asian Network for Development and Environmental Economics (SAMDEE)

Bolderdijk JW et al (2013) Comparing the effectiveness of monetary versus moral motives in environmental campaigning. Nat Clim Chang 3(4):413–416

Benartzi S et al (2017) Should governments invest more in nudging? Psychol Sci 28(8):1041–1055

Campaign (2019). https://www.campaignlive.co.uk/article/iceland-md-richard-walker-no-idea-rang-tan-film-blocked-tv/1578724

Peacock M, et al. (2019) Recycle, Reuse, Renew: food packaging pledges and promises in the fight against plastic pollution

Hoskins R (2008) Ban the plastic bag: a community action plan for a carrier bag free world. Penguin Books

GESAMP (2015) In: Kershaw PJ (ed) Sources, fate and effects of microplastics in the marine environment: a global assessment. IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP/ UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. p 96

Tankard ME, Paluck EL (2016) Norm perception as a vehicle for social change. Soc Issues Policy Rev 10(1):181–211

Cialdini RB, Reno RR, Kallgren CA (1990) A focus theory of normative conduct: recycling the concept of norms to reduce littering in public places. J Pers Soc Psychol 58(6):1015

Keizer K, Lindenberg S, Steg L (2013) The importance of demonstratively restoring order. PLoS One 8(6):e65137

Horcajo J, Briñol P, Petty RE (2014) Multiple roles for majority versus minority source status on persuasion when source status follows the message. Soc Influ 9(1):37–51

Prislin R, Christensen PN (2005) Social change in the aftermath of successful minority influence. Eur Rev Soc Psychol 16(1):43–73

Nemeth C, Swedlund M, Kanki B (1974) Patterning of the minority’s responses and their influence on the majority. Eur J Soc Psychol 4(1):53–64

Moscovici S, Nemeth C (1974) Social influence: II. Minority influence

Clark RD, Maass A (1988) Social categorization in minority influence: the case of homosexuality. Eur J Soc Psychol 18(4):347–364

Smith LG, Thomas EF, McGarty C (2015) “We must be the change we want to see in the world”: integrating norms and identities through social interaction. Polit Psychol 36(5):543–557

Anderson A et al (2016) Microplastics in personal care products: exploring perceptions of environmentalists, beauticians and students. Mar Pollut Bull 113(1–2):454–460

Bergmann M et al (2017) Citizen scientists reveal: marine litter pollutes Arctic beaches and affects wild life. Mar Pollut Bull 125(1):535–540

Evans J, Jones P (2011) The walking interview: methodology, mobility and place. Appl Geogr 31(2):849–858

Henderson L, Green C (2020) Making sense of microplastics? Public understandings of plastic pollution. Mar Pollut Bull 152:110908

Troschinetz AM, Mihelcic JR (2009) Sustainable recycling of municipal solid waste in developing countries. Waste Manag 29(2):915–923

Wyles KJ et al (2019) An evaluation of the fishing for litter (FFL) scheme in the UK in terms of attitudes, behavior, barriers and opportunities. Mar Pollut Bull 144:48–60

Hartley BL et al (2018) Exploring public views on marine litter in Europe: perceived causes, consequences and pathways to change. Mar Pollut Bull 133:945–955

Oppenheim AN (2000) Questionnaire design, interviewing and attitude measurement. Bloomsbury Publishing

Sheeran P, Webb TL (2016) The intention–behavior gap. Soc Personal Psychol Compass 10(9):503–518

Kormos C, Gifford R (2014) The validity of self-report measures of proenvironmental behavior: a meta-analytic review. J Environ Psychol 40:359–371

Martin L et al (2020) Nature contact, nature connectedness and associations with health, wellbeing and pro-environmental behaviours. J Environ Psychol 68:101389

Jakovcevic A et al (2014) Charges for plastic bags: motivational and behavioral effects. J Environ Psychol 40:372–380

Schultz PW et al (2013) Littering in context: personal and environmental predictors of littering behavior. Environ Behav 45(1):35–59

Hartley BL, Thompson RC, Pahl S (2015) Marine litter education boosts children’s understanding and self-reported actions. Mar Pollut Bull 90(1–2):209–217

Abrahamse W, Steg L (2013) Social influence approaches to encourage resource conservation: a meta-analysis. Glob Environ Chang 23(6):1773–1785

McKenzie-Mohr D (2013) Fostering sustainable behavior: an introduction to community-based social marketing. New Society Publishers

Peters G-JY, Ruiter RA, Kok G (2013) Threatening communication: a critical re-analysis and a revised meta-analytic test of fear appeal theory. Health Psychol Rev 7(Supp 1):S8–S31

Steg L, Vlek C (2009) Encouraging pro-environmental behaviour: an integrative review and research agenda. J Environ Psychol 29(3):309–317

Nuojua S, Pahl S, Thompson RC (2020) Ocean connectedness and consumer responses to single-use packaging. Manuscript under review

Nolan JM et al (2008) Normative social influence is underdetected. Personal Soc Psychol Bull 34(7):913–923

Wyles KJ (In Press) An issue buried under the ice? National survey examining people's perceptions to marine plastic waste in the Arctic and its influence on their plastic behaviour. Manuscript in preparation

Klöckner CA (2013) A comprehensive model of the psychology of environmental behaviour—a meta-analysis. Glob Environ Chang 23(5):1028–1038

Kahneman D (2011) Thinking, fast and slow. Farrar, Straus and Giroux, New York

De Groot JI, Steg L (2008) Value orientations to explain beliefs related to environmental significant behavior: how to measure egoistic, altruistic, and biospheric value orientations. Environ Behav 40(3):330–354

Heidbreder LM et al (2019) Tackling the plastic problem: a review on perceptions, behaviors, and interventions. Sci Total Environ 668:1077–1093

O'Connor RT et al (2010) Effects of number and location of bins on plastic recycling at a university. J Appl Behav Anal 43(4):711–715

Varotto A, Spagnolli A (2017) Psychological strategies to promote household recycling. A systematic review with meta-analysis of validated field interventions. J Environ Psychol 51:168–188

Geiger JL et al (2019) A meta-analysis of factors related to recycling. J Environ Psychol 64:78–97

Van Eygen E, Laner D, Fellner J (2018) Circular economy of plastic packaging: current practice and perspectives in Austria. Waste Manag 72:55–64

Ohtomo S, Ohnuma S (2014) Psychological interventional approach for reduce resource consumption: reducing plastic bag usage at supermarkets. Resour Conserv Recycl 84:57–65

Rivers N, Shenstone-Harris S, Young N (2017) Using nudges to reduce waste? The case of Toronto’s plastic bag levy. J Environ Manag 188:153–162

Poortinga W, Whitmarsh L, Suffolk C (2013) The introduction of a single-use carrier bag charge in Wales: attitude change and behavioural spillover effects. J Environ Psychol 36:240–247

Dorn M, Stöckli S (2018) Social influence fosters the use of a reusable takeaway box. Waste Manag 79:296–301

Lawman HG et al (2020) Peer reviewed: hydrate philly: an intervention to increase water access and appeal in recreation centers. Prev Chronic Dis 17

Poortinga W, Whitaker L (2018) Promoting the use of reusable coffee cups through environmental messaging, the provision of alternatives and financial incentives. Sustainability 10(3):873

Nelms S et al (2017) Marine anthropogenic litter on British beaches: a 10-year nationwide assessment using citizen science data. Sci Total Environ 579:1399–1409

Wyles KJ, Pahl S, Holland M, Thompson RC (2017) Can beach cleans do more than clean-up litter? Comparing beach cleans to other coastal activities. Environ Behav 49:509–535. https://doi.org/10.1177/0013916516649412

Schofield J et al (2020) Object narratives as a methodology for mitigating marine plastic pollution: multidisciplinary investigations in Galápagos. Antiquity 94(373):228–244

Lawson DF et al (2019) Children can foster climate change concern among their parents. Nat Clim Chang 9(6):458–462

DiCenso A et al (2002) Interventions to reduce unintended pregnancies among adolescents: systematic review of randomised controlled trials. Br Med J 324(7351):1426

Dilkes-Hoffman L et al (2019) Public attitudes towards bioplastics–knowledge, perception and end-of-life management. Resour Conserv Recycl 151:104479

Fletcher S et al (2009) Public awareness of marine environmental issues in the UK. Mar Policy 33(2):370–375

Gelcich S et al (2014) Public awareness, concerns, and priorities about anthropogenic impacts on marine environments. Proc Natl Acad Sci 111(42):15042–15047

Scott N, Parsons E (2005) A survey of public opinion in south-West Scotland on cetacean conservation issues. Aquat Conserv Mar Freshwat Ecosyst 15(3):299–312

EU Open Data Portal, Special Eurobarometer 501: Attitudes of European citizens towards the Environment (2020) European Commission, Brussels

Davison et al. Public concern about, and desire for research into, the human health effects of marine plastic pollution: Results from a 15-country survey across Europe and Australia. Manuscript in preparation

McCright AM, Dunlap RE (2011) The politicization of climate change and polarization in the American public's views of global warming, 2001–2010. Sociol Q 52(2):155–194

Slovic P (1999) Trust, emotion, sex, politics, and science: surveying the risk-assessment battlefield. Risk Anal 19(4):689–701

CAS   Google Scholar  

Spence A, Poortinga W, Pidgeon N (2012) The psychological distance of climate change. Risk Anal 32(6):957–972

White MP, Eiser JR (2006) Marginal trust in risk managers: building and losing trust following decisions under uncertainty. Risk Anal 26(5):1187–1203

Klöckner CA (2015) The psychology of pro-environmental communication: beyond standard information strategies. Palgrave Macmillan, New York

Plous S (1993) The psychology of judgment and decision making. Mcgraw-Hill

Böhm G, Tanner C (2018) Environmental risk perception. In: Steg L, Groot JIM (eds) Environmental psychology, pp 13–25

Chapter   Google Scholar  

Kasperson RE, Kasperson JX (1996) The social amplification and attenuation of risk. Ann Am Acad Pol Soc Sci 545(1):95–105

Morgan MG et al (2002) Risk communication: a mental models approach. Cambridge University Press, Cambridge

Arnett JJ (2016) The neglected 95%: why American psychology needs to become less American. Am Psychol 63(7):602–614

Henrich J, Heine SJ, Norenzayan A (2010) Most people are not WEIRD. Nature 466(7302):29–29

Henrich J, Heine SJ, Norenzayan A (2010) The weirdest people in the world? Behav Brain Sci 33(2–3):61–83

Simmons EC, Fielding KS (2019) Psychological predictors of fishing and waste management intentions in Indonesian coastal communities. J Environ Psychol 65:101324

Van der Linden S (2015) The social-psychological determinants of climate change risk perceptions: towards a comprehensive model. J Environ Psychol 41:112–124

Goldstein N, Cialdini RB, Griskevicius V (2008) A room with a viewpoint: using social norms to motivate environmental conservation in hotels. J Consum Res 35(3):472–482

Singhirunnusorn W, Donlakorn K, Kaewhanin W (2012) Contextual factors influencing household recycling behaviours: a case of waste bank project in Mahasarakham municipality. Procedia Soc Behav Sci 36:688–697

Ajzen I (1991) The theory of planned behavior. Organ Behav Hum Decis Process 50:179–211

Pakpour AH et al (2014) Household waste behaviours among a community sample in Iran: an application of the theory of planned behaviour. Waste Manag 34(6):980–986

Thongpila K (2019) Fabricated future: applying the theory of planned behavior to influence purchase intention of green fashion made from recycled plastic in Thailand, in textile management. University of Boras, Boras

Halder P, Singh H (2018) Predictors of recycling intentions among the youth: a developing country perspective. Recycling 3(3):38

Mtutu P, Thondhlana G (2016) Encouraging pro-environmental behaviour: energy use and recycling at Rhodes University, South Africa. Habitat Int 53:142–150

Bratt C (1999) The impact of norms and assumed consequences on recycling behavior. Environ Behav 31(5):630–656

Schultz PW (2002) Knowledge, information, and household recycling: Examining the knowledge-deficit model of behavior change. New tools for environmental protection: Education, information, and voluntary measures. pp 67–82

Afroz R et al (2010) A survey of recycling behaviour in households in Dhaka, Bangladesh. Waste Manag Res 28(6):552–560

Akil AM, Foziah J, Ho CS (2015) The effects of socio-economic influences on households recycling behaviour in Iskandar Malaysia. Procedia Soc Behav Sci 202:124–134

Miafodzyeva S, Brandt N (2013) Recycling behaviour among householders: synthesizing determinants via a meta-analysis. Waste Biomass Valorization 4(2):221–235

Rist S et al (2018) A critical perspective on early communications concerning human health aspects of microplastics. Sci Total Environ 626:720–726

Wardman T, Koelmans AA, Whyte J, Pahl S (2010) Communicating the absence of evidence for microplastics risk: balancing sensation and reflection. Environ Int:106116, ISSN 0160–4120. https://doi.org/10.1016/j.envint.2020.106116 . http://www.sciencedirect.com/science/article/pii/S0160412020320717

Rozin P, Royzman EB (2001) Negativity bias, negativity dominance, and contagion. Personal Soc Psychol Rev 5(4):296–320

Richter I, Thøgersen J, Klöckner CA (2018) A social norms intervention going wrong: boomerang effects from descriptive norms information. Sustainability 10(8):2848

Newman S et al (2015) The economics of marine litter. In: Marine anthropogenic litter. Springer, Cham, pp 367–394

Czigány T, Ronkay F (2020) The coronavirus and plastics. Express Polym Lett 14(6):510–511

Prata JC et al (2020) COVID-19 pandemic repercussions on the use and management of plastics. Environ Sci Technol

Thompson RC, Pahl S. University of Plymouth. Unpublished data

Dietz T et al (2009) Household actions can provide a behavioral wedge to rapidly reduce US carbon emissions. Proc Natl Acad Sci 106(44):18452–18456

Rogers EM (2003) Diffusion of innovations. Free Press, New York

Download references

Author information

Authors and affiliations.

School of Psychology and Marine Institute, University of Plymouth, Plymouth, UK

Sabine Pahl, Isabel Richter & Kayleigh Wyles

Urban and Environmental Psychology Group, Faculty of Psychology, University of Vienna, Vienna, Austria

Sabine Pahl

University of Surrey, Surrey, UK

Kayleigh Wyles

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Sabine Pahl .

Editor information

Editors and affiliations.

German Federal Institute of Hydrology, Koblenz, Germany

Friederike Stock

Georg Reifferscheid

Nicole Brennholt

P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

Evgeniia Kostianaia

Rights and permissions

Reprints and permissions

Copyright information

© 2020 Springer Nature Switzerland AG

About this chapter

Cite this chapter.

Pahl, S., Richter, I., Wyles, K. (2020). Human Perceptions and Behaviour Determine Aquatic Plastic Pollution. In: Stock, F., Reifferscheid, G., Brennholt, N., Kostianaia, E. (eds) Plastics in the Aquatic Environment - Part II. The Handbook of Environmental Chemistry, vol 112. Springer, Cham. https://doi.org/10.1007/698_2020_672

Download citation

DOI : https://doi.org/10.1007/698_2020_672

Published : 26 October 2020

Publisher Name : Springer, Cham

Print ISBN : 978-3-030-84113-3

Online ISBN : 978-3-030-84114-0

eBook Packages : Chemistry and Materials Science Chemistry and Material Science (R0)

Share this chapter

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Publish with us

Policies and ethics

• Find a journal
• Track your research

Ocean floor a 'reservoir' of plastic pollution

New research from CSIRO, Australia's national science agency, and the University of Toronto in Canada, estimates up to 11 million tonnes of plastic pollution is sitting on the ocean floor.

Every minute, a garbage truck's worth of plastic enters the ocean. With plastic use expected to double by 2040, understanding how and where it travels is crucial to protecting marine ecosystems and wildlife.

Dr Denise Hardesty, Senior Research Scientist with CSIRO, said this is the first estimate of how much plastic waste ends up on the ocean floor, where it accumulates before being broken down into smaller pieces and mixed into ocean sediment.

"We know that millions of tonnes of plastic waste enter our oceans every year but what we didn't know is how much of this pollution ends up on our ocean floor," Dr Hardesty said.

"We discovered that the ocean floor has become a resting place, or reservoir, for most plastic pollution, with between 3 to 11 million tonnes of plastic estimated to be sinking to the ocean floor.

"While there has been a previous estimate of microplastics on the seafloor, this research looks at larger items, from nets and cups to plastic bags and everything in between."

Ms Alice Zhu, a PhD Candidate from the University of Toronto who led the study, said the estimate of plastic pollution on the ocean floor could be up to 100 times more than the amount of plastic floating on the ocean's surface based on recent estimates.

"The ocean surface is a temporary resting place of plastic so it is expected that if we can stop plastic entering our oceans, the amount would be reduced," Ms Zhu said.

"However, our research found that plastic will continue to end up in the deep ocean, which becomes a permanent resting place or sink for marine plastic pollution,"

Scientific data was used to build two predictive models to estimate the amount and distribution of plastic on the ocean floor -- one based on data from remote operated vehicles (ROVs) and the other from bottom trawls.

Using ROV data, 3 to 11 million metric tonnes of plastic pollution is estimated to reside on the ocean floor.

The ROV results also reveal that plastic mass clusters around continents -- approximately half (46 per cent) of the predicted plastic mass on the global ocean floor resides above 200 m depth. The ocean depths, from 200 m to as deep as 11,000 m contains the remainder of predicted plastic mass (54 per cent).

Although inland and coastal seas cover much less surface area than oceans (11 per cent vs 56 per cent out of the entire Earth's area), these areas are predicted to hold as much plastic mass as does the rest of the ocean floor.

"These findings help to fill a longstanding knowledge gap on the behaviour of plastic in the marine environment," Ms Zhu said.

"Understanding the driving forces behind the transport and accumulation of plastic in the deep ocean will help to inform source reduction and environmental remediation efforts, thereby reducing the risks that plastic pollution may pose to marine life."

The article, Plastics in the deep sea -- A global estimate of the ocean floor reservoir , was published in Deep Sea Research Part I: Oceanographic Research Papers.

This research is part of CSIRO's Ending Plastic Waste Mission, which aims to change the way we make, use, recycle and dispose of plastic.

• Oceanography
• Environmental Awareness
• Recycling and Waste
• Environmental Issues
• Earth Science
• Oceanic trench
• Hazardous waste
• Radioactive waste

Story Source:

Materials provided by CSIRO Australia . Note: Content may be edited for style and length.

Journal Reference :

• Xia Zhu, Chelsea M. Rochman, Britta Denise Hardesty, Chris Wilcox. Plastics in the deep sea – A global estimate of the ocean floor reservoir . Deep Sea Research Part I: Oceanographic Research Papers , 2024; 206: 104266 DOI: 10.1016/j.dsr.2024.104266

Cite This Page :

Explore More

• 3D Mouth of an Ancient Jawless Fish
• Connecting Lab-Grown Brain Cells
• Device: Self-Healing Materials, Drug Delivery
• How We Perceive Bitter Taste
• Next-Generation Digital Displays
• Feeling Insulted? How to Rid Yourself of Anger
• Pregnancy Accelerates Biological Aging
• Tiny Plastic Particles Are Found Everywhere
• What's Quieter Than a Fish? A School of Them
• Do Odd Bones Belong to Gigantic Ichthyosaurs?

Trending Topics

Strange & offbeat.

share this!

April 5, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

trusted source

Ocean floor a 'reservoir' of plastic pollution, study finds

New research from CSIRO, Australia's national science agency, and the University of Toronto in Canada, estimates up to 11 million metric tons of plastic pollution is sitting on the ocean floor. The article, "Plastics in the deep sea—A global estimate of the ocean floor reservoir ," was published in Deep Sea Research Part I: Oceanographic Research Papers.

Every minute, a garbage truck's worth of plastic enters the ocean. With plastic use expected to double by 2040, understanding how and where it travels is crucial to protecting marine ecosystems and wildlife.

Dr. Denise Hardesty, Senior Research Scientist with CSIRO, said this is the first estimate of how much plastic waste ends up on the ocean floor , where it accumulates before being broken down into smaller pieces and mixed into ocean sediment.

"We know that millions of tons of plastic waste enter our oceans every year but what we didn't know is how much of this pollution ends up on our ocean floor," Dr. Hardesty said.

"We discovered that the ocean floor has become a resting place, or reservoir, for most plastic pollution, with between 3 to 11 million tons of plastic estimated to be sinking to the ocean floor.

"While there has been a previous estimate of microplastics on the seafloor, this research looks at larger items, from nets and cups to plastic bags and everything in between."

Alice Zhu, a Ph.D. Candidate from the University of Toronto who led the study, said the estimate of plastic pollution on the ocean floor could be up to 100 times more than the amount of plastic floating on the ocean's surface based on recent estimates.

"The ocean surface is a temporary resting place of plastic so it is expected that if we can stop plastic entering our oceans, the amount would be reduced," Zhu said.

"However, our research found that plastic will continue to end up in the deep ocean, which becomes a permanent resting place or sink for marine plastic pollution."

Scientific data was used to build two predictive models to estimate the amount and distribution of plastic on the ocean floor—one based on data from remote operated vehicles (ROVs) and the other from bottom trawls.

Using ROV data, 3 to 11 million metric tons of plastic pollution is estimated to reside on the ocean floor.

The ROV results also reveal that plastic mass clusters around continents—approximately half (46%) of the predicted plastic mass on the global ocean floor resides above 200 m depth. The ocean depths, from 200 m to as deep as 11,000 m contains the remainder of predicted plastic mass (54%).

Although inland and coastal seas cover much less surface area than oceans (11% vs. 56% out of the entire Earth's area), these areas are predicted to hold as much plastic mass as does the rest of the ocean floor.

"These findings help to fill a longstanding knowledge gap on the behavior of plastic in the marine environment ," Zhu said.

"Understanding the driving forces behind the transport and accumulation of plastic in the deep ocean will help to inform source reduction and environmental remediation efforts, thereby reducing the risks that plastic pollution may pose to marine life."

This research is part of CSIRO's Ending Plastic Waste Mission , which aims to change the way we make, use, recycle and dispose of plastic.

Provided by CSIRO

Explore further

Feedback to editors

Using CO₂ and biomass, researchers find path to more environmentally friendly recyclable plastics

9 hours ago

Precision agriculture research identifies gene that controls production of flowers and fruits in pea plants

Long-term forest study shows tornado's effects linger 25 years later

10 hours ago

A new coating method in mRNA engineering points the way to advanced therapies

ATLAS provides first measurement of the W-boson width at the LHC

11 hours ago

Smart vest turns fish into underwater spies, providing a glimpse into aquatic life like never before

Ants in Colorado are on the move due to climate change

Caterpillar 'noses' are surprisingly sophisticated, researchers find

Building footprints could help identify neighborhood sociodemographic traits

12 hours ago

Fossilized dinosaur eggshells can preserve amino acids, the building blocks of proteins, over millions of years

13 hours ago

Relevant PhysicsForums posts

Iceland warming up again - quakes swarming.

Apr 9, 2024

M 4.8 - Whitehouse Station, New Jersey, US

Apr 6, 2024

Major Earthquakes - 7.4 (7.2) Mag and 6.4 Mag near Hualien, Taiwan

Apr 5, 2024

Unlocking the Secrets of Prof. Verschure's Rosetta Stones

‘our clouds take their orders from the stars,’ henrik svensmark on cosmic rays controlling cloud cover and thus climate.

Mar 27, 2024

Higher Chance to get Lightning Strike by Large Power Consumption?

Mar 20, 2024

More from Earth Sciences

Related Stories

Plastic litter in oceans overestimated but could persist longer than expected, study suggests

Aug 7, 2023

Thousands of tons of microplastics found in Moreton Bay

Mar 25, 2024

14 million tonnes of microplastics on sea floor: Australian study

Oct 7, 2020

International Environment Day: Plastic in Africa

Jun 4, 2018

Video: Keeping an eye on ocean plastic pollution from space

Aug 12, 2021

Visible ocean plastics just the tip of the iceberg

Mar 18, 2022

Recommended for you

US announces tough tap water standards for 'forever chemicals'

14 hours ago

Humans shape the journey of mud, study reveals

15 hours ago

Broken record: March is 10th straight month to be hottest on record, scientists say

Humans have converted at least 250,000 acres of estuaries to cities and farms in last 35 years, study finds

Hurricane risk perception drops after storms hit, study shows

Heat from El Niño can warm oceans off West Antarctica—and melt floating ice shelves from below

Let us know if there is a problem with our content.

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

News from the Columbia Climate School

Protecting Our Planet: 5 Strategies for Reducing Plastic Waste

Olga Rukovets

Plastics are ubiquitous in our world, and given that plastic waste can take thousands of years to break down , there’s more of it to be found on Earth every single day. Worse yet is the fact that the stuff doesn’t easily decompose —it mostly just disintegrates into smaller and smaller pieces.

These tiny particles, called microplastics , have found their way to all parts of our globe , no matter how remote. They’re also increasingly detected in our food and drinking water. A recent study by Columbia researchers found that water bottles contain even more—10 to 100 times more—of these minute plastic bits (dubbed “nanoplastics”) than we previously believed. The health effects and downstream repercussions of microplastics are not fully understood, but researchers are concerned about the long-term impacts of ingesting all this plastic.

Meaningful change to clean up this mess will undoubtedly need to happen on a very large scale. Accordingly, Earthday.org , an organization that originates from the first Earth Day back in 1970, has designated this year’s theme as Planet vs. Plastics , with a goal of achieving a 60% reduction in plastics production by 2040. Organizations like Ocean Cleanup have been working on technologies to clean up the plastic floating in our oceans and polluting our waterways. And in 2022, 175 UN member nations signed on to a global agreement that promises to produce a binding treaty to overcome the scourge of plastic by the end of this year (though it has not been without setbacks ).

What are some actions individuals can take on a regular basis to reduce plastics consumption?

1. Embrace the circular economy

Increasingly, advocates are calling for a circular approach to production and consumption as one important way to reduce the burden of plastic waste. Sandra Goldmark , senior assistant dean of interdisciplinary engagement at the Columbia Climate School, reminds us that circularity is very much in use in the modern world—we have public libraries, neighborhood swaps and traditional and regenerative agricultural practices that demonstrate the success of the concept. But it does need to be harnessed on a global scale for the benefits to be palpable. “Currently [our economy] is just 8.6% circular,” Goldmark said. “Over 90% of the resources extracted from the earth are manufactured into goods that are used, usually once, and then sent to landfill or incinerated, often within a year.” By encouraging greater reuse, repurposing and exchange of these goods, we can keep more plastic out of our oceans and reduce global greenhouse gas emissions substantively.

Fast fashion, for example, may be appealing for its convenience and low prices—but what are the true costs? With 100 billion garments being produced every year, 87% end up as waste ( 40 million tons ) in a landfill or incinerator. The average person is now buying 60 percent more clothing than they did 15 years ago, but they’re only keeping them for  half as long as they used to, according to EarthDay.org . 

Instead, the UN Environment Programme recommends re-wearing clothes more frequently and washing them less often. Look for neighborhood swaps and Buy Nothing groups, where you can trade items with your local community. Consider repairing items before trading them in for new ones. See additional tips for healthier consumption of “stuff” here .

2. Reduce your reliance on single-use plastics

Considering the fact that Americans currently purchase about 50 billion water bottles per year, switching to a reusable water bottle could save an average of 156 plastic bottles annually. Start bringing reusable shopping bags and containers when you go to the grocery store or coffee shop.

Many cities and states have already implemented plastic bag bans as one step toward decreasing our use of these plastics. Some local businesses even offer discounts for bringing your own coffee cup or bags with you.

3. If all else fails, recycle (responsibly)

When it can’t be avoided, recycle your plastic correctly . If you try to recycle the wrong items—sometimes called “ wishcycling ”—it can slow down an already constrained sorting process. One rule to remember, Keefe Harrison, CEO of the Recycling Partnership , told NPR: “When in doubt, leave it out.”

Recycling programs vary between communities and states, so it’s important to get to know your symbols and research what they mean in your own zip code . For example , plastic bags and plastic wrap or film cannot be placed in your household recycling bin, but some stores have special collections for those items. The symbol on the bottom of a plastic container can tell you what the plastic is made from, which can help guide your decision to recycle it or not, but it doesn’t necessarily mean it can be picked up by your local recycling program. Local websites, like New York City’s 311 , can provide a more detailed breakdown of the types of items that can and cannot be recycled—e.g., rigid plastic packaging including “clamshells”: yes; tubes from cosmetics and toothpaste: no.

Still, reports of how much (or how little) of our plastic waste is actually recycled are alarming—with some estimates ranging from 10% to as low as 5% —so it is still best to opt for other alternatives whenever possible.

4. Get involved with local actions and clean-ups

There are many local movements doing their part to mitigate the environmental contamination caused by plastics pollution. Take a look at what’s happening locally in your neighborhood and globally. Check with your parks department for organized community efforts or consider starting your own . As part of EarthDay.org, you can register your initiative with the Great Global Cleanup , where you can find helpful tips on all stages of this process and connect with a worldwide community.

5. Stay informed about new legislation

As the world grapples with the growing plastics crisis, some states are trying to take matters into their own hands. In California, the Plastic Pollution Prevention and Packaging Producer Responsibility Act (known as SB 54 ), mandates the switch to compostable packaging for all single-use utensils, containers and other receptacles by 2032, with steep fines for companies that don’t comply. New York is currently moving ahead with a bill called Packaging Reduction and Recycling Infrastructure Act , with the goal of cutting down plastic packaging by 50% in the next 12 years; if it is signed into law, this legislation would also mandate charging fees for noncompliant brands.

Pay attention to what’s happening in your own county, state or country and get involved with efforts to advocate for causes you support. Send messages to your representatives, educate your neighbors and friends, and join a larger contingent of people trying to make the world a better and more sustainable place for current and future generations.

Related Posts

Was It an Alien Spacecraft—Or a Delivery Truck?

A Virtual Reality Film That Makes the Climate Crisis Feel “Real”

This Earth Day, Choose the Planet Over Plastics

Celebrate over 50 years of Earth Day with us all month long! Visit our Earth Day website for ideas, resources, and inspiration.

Get the Columbia Climate School Newsletter →