Mark Anthony Browne

Policy: Classify plastic waste as hazardous

Policies for managing plastic debris are outdated and threaten the health of people and wildlife, say Chelsea M. Rochman, Mark Anthony Browne and colleagues.

Microplastic Moves Pollutants and Additives to Worms, Reducing Functions Linked to Health and Biodiversity

Inadequate products, waste management, and policy are struggling to prevent plastic waste from infiltrating ecosystems [1, 2]. Disintegration into smaller pieces means that the abundance of micrometer-sized plastic (microplastic) in habitats has increased [3] and outnumbers larger debris [2, 4]. When ingested by animals, plastic provides a feasible pathway to transfer attached pollutants and additive chemicals into their tissues [5-15]. Despite positive correlations between concentrations of ingested plastic and pollutants in tissues of animals, few, if any, controlled experiments have examined whether ingested plastic transfers pollutants and additives to animals. We exposed lugworms (Arenicola marina) to sand with 5% microplastic that was presorbed with pollutants (nonylphenol and phenanthrene) and additive chemicals (Triclosan and PBDE-47). Microplastic transferred pollutants and additive chemicals into gut tissues of lugworms, causing some biological effects, although clean sand transferred larger concentrations of pollutants into their tissues. Uptake of nonylphenol from PVC or sand reduced the ability of coelomocytes to remove pathogenic bacteria by >60%. Uptake of Triclosan from PVC diminished the ability of worms to engineer sediments and caused mortality, each by >55%, while PVC alone made worms >30% more susceptible to oxidative stress. As global microplastic contamination accelerates, our findings indicate that large concentrations of microplastic and additives can harm ecophysiological functions performed by organisms.

The ecological impacts of marine debris: unraveling the demonstrated evidence from what is perceived

Anthropogenic debris contaminates marine habitats globally, leading to several perceived ecological impacts. Here, we critically and systematically review the literature regarding impacts of debris from several scientific fields to understand the weight of evidence regarding the ecological impacts of marine debris. We quantified perceived and demonstrated impacts across several levels of biological organization that make up the ecosystem and found 366 perceived threats of debris across all levels. Two hundred and ninety-six of these perceived threats were tested, 83% of which were demonstrated. The majority (82%) of demonstrated impacts were due to plastic, relative to other materials (e.g., metals, glass) and largely (89%) at suborganismal levels (e.g., molecular, cellular, tissue). The remaining impacts, demonstrated at higher levels of organization (i.e., death to individual organisms, changes in assemblages), were largely due to plastic marine debris (> 1 mm; e.g., rope, straws, and fragments). Thus, we show evidence of ecological impacts from marine debris, but conclude that the quantity and quality of research requires improvement to allow the risk of ecological impacts of marine debris to be determined with precision. Still, our systematic review suggests that sufficient evidence exists for decision makers to begin to mitigate problematic plastic debris now, to avoid risk of irreversible harm.

Linking effects of anthropogenic debris to ecological impacts

Accelerated contamination of habitats with debris has caused increased effort to determine ecological impacts. Strikingly, most work on organisms focuses on sublethal responses to plastic debris. This is controversial because (i) researchers have ignored medical insights about the mechanisms that link effects of debris across lower levels of biological organization to disease and mortality, and (ii) debris is considered non-hazardous by policy-makers, possibly because individuals can be injured or removed from populations and assemblages without ecological impacts. We reviewed the mechanisms that link effects of debris across lower levels of biological organization to assemblages and populations. Using plastic, we show microplastics reduce the ‘health’, feeding, growth and survival of ecosystem engineers. Larger debris alters assemblages because fishing-gear and tyres kill animals and damage habitat-forming plants, and because floating bottles facilitate recruitment and survival of novel taxa. Where ecological linkages are not known, we show how to establish hypothetical links by synthesizing studies to assess the likelihood of impacts. We also consider how population models examine ecological linkages and guide management of ecological impacts. We show that by focusing on linkages to ecological impacts rather than the presence of debris and its sublethal impacts, we could reduce threats posed by debris.

Sources and Pathways of Microplastics to Habitats

Identifying and eliminating the sources of microplastic to habitats is crucial to reducing the social, environmental and economic impacts of this form of debris. Although eliminating sources of pollution is a fundamental component of environmental policy in the U.S.A. and Europe, the sources of microplastic and their pathways into habitats remain poorly understood compared to other persistent, bioaccumulative and/or toxic substances (i.e. priority pollutants; EPA in U.S. Environmental Protection Agency 2010–2014 Pollution Prevention (P2) Program Strategic Plan. Washington, USA, pp. 1–34, 2010; EU in Official J Eur Union L334:17–119, 2010). This chapter reviews our understanding of sources and pathways of microplastic, appraises terminology, and outlines future directions for meaningfully integrating research, managerial actions and policy to understand and reduce the infiltration of microplastic to habitats.

Some problems and practicalities in design and interpretation of samples of microplastic waste

Plastic as waste-material is increasingly littering the worlds environments. Small particles of plastic – microplastics – are an increasing cause of concern because they can potentially cause a range of environmental problems for organisms and for the assemblages in which they live. Particles are a potential source of impacts in their own right, or as carriers of toxins that can then become absorbed into animals or plants. As a result, there has been increasing publication of programmes of sampling to quantify microplastics, to identify what types are where and to consider the extent to which they are causing impacts. Some of the sampling is to consider large-scale patterns. Some is to gather information about temporal trends. Regardless of the objectives, much of the sampling is not adequate to provide robust data to allow comparative assessments, examine trends or, in some cases, even to be sure about the quantities of plastic being encountered. The problems in such sampling programmes have been widely discussed in the ecological literature. Here, we attempt to identify some of the major problems and their causes and to promote thinking about the available solutions, in terms of improved sampling designs. This is done in the hope that more thought about the pitfalls will lead to more seeking of advice from statisticians and those who are expert in sampling, so that better information will become available in the future.

Direct and indirect effects of different types of microplastics on freshwater prey (Corbicula fluminea) and their predator (Acipenser transmontanus)

We examined whether environmentally relevant concentrations of different types of microplastics, with or without PCBs, directly affect freshwater prey and indirectly affect their predators. Asian clams (Corbicula fluminea) were exposed to environmentally relevant concentrations of polyethylene terephthalate (PET), polyethylene, polyvinylchloride (PVC) or polystyrene with and without polychlorinated biphenyls (PCBs) for 28 days. Their predators, white sturgeon (Acipenser transmontanus), were exposed to clams from each treatment for 28 days. In both species, we examined bioaccumulation of PCBs and effects (i.e., immunohistochemistry, histology, behavior, condition, mortality) across several levels of biological organization. PCBs were not detected in prey or predator, and thus differences in bioaccumulation of PCBs among polymers and biomagnification in predators could not be measured. One of the main objectives of this study was to test the hypothesis that bioaccumulation of PCBs would differ among polymer types. Because we could not answer this question experimentally, a bioaccumulation model was run and predicted that concentrations of PCBs in clams exposed to polyethylene and polystyrene would be greater than PET and PVC. Observed effects, although subtle, seemed to be due to microplastics rather than PCBs alone. For example, histopathology showed tubular dilation in clams exposed to microplastics with PCBs, with only mild effects in clams exposed to PCBs alone.

Organophosphorous biocides reduce tenacity and cellular viability but not esterase activities in a non-target prosobranch (limpet).

Detecting impacts of organophosphorus biocides (OP) is facilitated by analysing biomarkers - biological responses to environmental insults. Understanding is hampered by studying biomarkers in isolation at different levels of biological response and limited work on ecologically-important species. We tested the relevance of esterases as biomarkers of OP-exposure in limpets (Patella vulgata), abundant prosobranchs that structure the assemblages on rocky shores through their grazing. We characterized esterases in haemolymph and tissue, and quantified their dose-dependent inhibition by chlorfenvinphos (0.1-3.0 mM) in vitro. To determine whether esterases are useful biomarkers we exposed limpets to chlorfenvinphos (0-10 μg L(-1)). Despite reduced tenacity (ability to stick to a surface) and haemocyte-viability, esterases remained unaffected. Tenacity was reduced by >50% at 5 μg L(-1) and by 95% at 10 μg L(-1), whilst haemocyte-viability was more sensitive with >40% reductions at concentrations of 0.5 μg L(-1) and above. We discuss results in relation to linking sub-lethal and ecological impacts at contaminated sites.

What Do We Know About the Ecological Impacts of Microplastic Debris

C.M. Rochman, M.A. Browne, A.J. Underwood, J.A. van Franeker, R.C. Thompson and L.A. Amaral-Zettler University of California, Davis, CA, United States University of California, Santa Barbara, CA United States University of New South Wales, Sydney, NSW, Australia University of Sydney, Sydney, NSW, Australia Institute for Marine Research and Ecosystem Studies IMARES, Texel, The Netherlands Plymouth University, Plymouth, United Kingdom Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Woods Hole, MA, United States Brown University, Providence, RI, United States