A meta-analysis of the effects of exposure to microplastics on fish and aquatic invertebrates

Microplastics are present in aquatic ecosystems the world over and may influence the feeding, growth, reproduction, and survival of freshwater and marine biota; however, the extent and magnitude of potential effects of microplastics on aquatic organisms is poorly understood. In the current study, we conducted a meta-analysis of published literature to examine impacts of exposure to microplastics on consumption (and feeding), growth, reproduction, and survival of fish and aquatic invertebrates. While we did observe within-taxa negative effects for all four categories of responses, many of the effects summarized in our study were neutral, indicating that the effects of exposure to microplastics are highly variable across taxa. The most consistent effect was a reduction in consumption of natural prey when microplastics were present. For some taxa, negative effects on growth, reproduction and even survival were also evident. Organisms that serve as prey to larger predators, e.g., zooplankton, may be particularly susceptible to negative impacts of exposure to microplastic pollution, with potential for ramifications throughout the food web. Future work should focus on whether microplastics may be affecting aquatic organisms more subtly, e.g., by influencing exposure to contaminants and pathogens, or by acting at a molecular level.

Carolyn J. Foley, Zachary S. Feiner, Timothy D. Malinich, Tomas O. Höök, Science of The Total Environment, Volumes 631–632, 1 August 2018, Pages 550–559

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Closing Microplastic Pathways Before They Open: A Model Approach

In a recent viewpoint paper, the issue of microplastic pollution was discussed with a view that the environmental threat of such pollution is overstated.1 While somewhat divisive, some ideas expressed (i.e., that ex-situ toxicology studies should examine microplastic-biota interactions at concentrations similar to what are recorded in natural environments) have considerable merit. However, one statement hinted at a more worrying stance for toxicologists to take. This was that the weight of research and media coverage of microplastics has led to adverse legislative moves, such as the ban on microbeads. While it is understandable that there are perhaps greater toxicological pollutants that are more deserving of legislative action, it is difficult to see this ban as an adverse move.

Alexander S. Tagg and Matthias Labrenz, Environ. Sci. Technol., Article ASAP, March 8, 2018

The article

Microplastics: No Small Problem for Filter-Feeding Megafauna

Microplastic pollution can impact filter-feeding marine megafauna, namely mobulid rays, filter-feeding sharks, and baleen whales. Emerging research on these flagship species highlights potential exposure to microplastic contamination and plastic-associated toxins. Research and its wide communication are needed to understand the magnitude of the issue and improve marine stewardship. (…)

Elitza S. Germanov, Andrea D. Marshall, Lars Bejder, Maria Cristina Fossi, Neil R. Loneragan, Trends in Ecology & Evolution, Available online 6 February 2018, In Press

The article

Microplastic Abundance and Composition in Western Lake Superior As Determined via Microscopy, Pyr-GC/MS, and FTIR

While plastic pollution in marine and freshwater systems is an active area of research, there is not yet an in-depth understanding of the distributions, chemical compositions, and fates of plastics in aquatic environments. In this study, the magnitude, distribution, and common polymers of microplastic pollution in surface waters in western Lake Superior are determined. Analytical methodology, including estimates of ambient contamination during sample collection and processing, are described and employed. Microscopy, pyrolysis-gas chromatography/mass spectrometry (Pyr-GC/MS), and Fourier transform infrared spectroscopy (FTIR) were used to quantify and identify microplastic particles. In surface waters, fibers were the most frequently observed morphology, and, based upon PyGC/MS analysis,  polyvinyl chloride was the most frequently observed polymer, followed by polypropylene and polyethylene. The most common polymer identified by FTIR was polyethylene. Despite the low human population in Lake Superior’s watershed, microplastic particles (particularly fibers, fragments, and films) were identified in western-lake surface waters at levels comparable to average values reported in studies within Lake Michigan, the North Atlantic Ocean, and the South Pacific Ocean. This study provides insight into the magnitude of microplastic pollution in western Lake Superior, and describes in detail methodology to improve future microplastics studies in aquatic systems.

Erik Hendrickson, Elizabeth C. Minor, and Kathryn Schreiner, Environ. Sci. Technol., Article ASAP, January 18, 2018

Microplastic Effect Thresholds for Freshwater Benthic Macroinvertebrates

Now that microplastics have been detected in lakes, rivers, and estuaries all over the globe, evaluating their effects on biota has become an urgent research priority. This is the first study that aims at determining the effect thresholds for a battery of six freshwater benthic macroinvertebrates with different species traits, using a wide range of microplastic concentrations. Standardized 28 days single species bioassays were performed under environmentally relevant exposure conditions using polystyrene microplastics (20–500 μm) mixed with sediment at concentrations ranging from 0 to 40% sediment dry weight (dw). Microplastics caused no effects on the survival of Gammarus pulex, Hyalella azteca, Asellus aquaticus, Sphaerium corneum, and Tubifex spp. and no effects were found on the reproduction of Lumbriculus variegatus. No significant differences in growth were found for H. azteca, A. aquaticus, S. corneum, L. variegatus, and Tubifex spp. However, G. pulex showed a significant reduction in growth (EC10 = 1.07% sediment dw) and microplastic uptake was proportional with microplastic concentrations in sediment. These results indicate that although the risks of environmentally realistic concentrations of microplastics may be low, they still may affect the biodiversity and the functioning of aquatic communities which after all also depend on the sensitive species.

Paula E. Redondo-Hasselerharm, Dede Falahudin, Edwin T. H. M. Peeters, and Albert A. Koelmans, Environ. Sci. Technol., Article ASAP, January 16, 2018

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Combined effects of microplastics and chemical contaminants on the organ toxicity of zebrafish (Danio rerio)

Microplastics contamination of the aquatic environment is considered a growing problem. The ingestion of microplastics has been documented for a variety of aquatic animals. Studies have shown the potential of microplastics to affect the bioavailability and uptake route of sorbed co-contaminants of different nature in living organisms. Persistent organic pollutants and metals have been the co-contaminants majorly investigated in this field. The combined effect of microplastics and sorbed co-contaminants in aquatic organisms still needs to be properly understood. To address this, we have subjected zebrafish to four different feeds: A) untreated feed; B) feed supplemented with microplastics (LD-PE 125–250 µm of diameter); C) feed supplemented with 2% microplastics to which a mixture of PCBs, BFRs, PFCs and methylmercury were sorbed; and D) feed supplemented with the mixture of contaminants only. After 3 weeks of exposure fish were dissected and liver, intestine, muscular tissue and brain were extracted. After visual observation, evaluation of differential gene expression of some selected biomarker genes in liver, intestine and brain were carried out. Additionally, quantification of perfluorinated compounds in liver, brain, muscular tissue and intestine of some selected samples were performed. The feed supplemented with microplastics with sorbed contaminants produced the most evident effects especially on the liver. The results indicate that microplastics alone does not produce relevant effects on zebrafish in the experimental conditions tested; on the contrary, the combined effect of microplastics and sorbed contaminants altered significantly their organs homeostasis in a greater manner than the contaminants alone.

Sandra Rainieri, Nadia Conlledo, Bodil K. Larsen, Kit Granby, Alejandro Barranco, Environmental Research, Volume 162, April 2018, Pages 135-143

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A revisited conceptualization of plastic pollution accumulation in marine environments: Insights from a social ecological economics perspective

The proliferation of synthetic polymer fragments in marine ecosystems has become a prominent issue within recent years, and its disastrous implications on marine species as well as associated social and economic costs have been extensively documented. A narrow perspective of analysis has characterized current conceptualizations of the phenomenon, which is further resembled in the proposed approaches to tackle the problem. Based on a critical realist philosophy of science, this article aims to investigate the fundamental and interdisciplinary dynamics underpinning the current production, consumption and post-consumption lifecycle of plastics, by abstracting transfactual relationships. These then provide the basis to develop a conceptual model for understanding the phenomenon in a more comprehensive manner, and form a framework to assess proposed policy responses for addressing the issue. Thereby the conceptual model draws upon four fields of knowledge: (i) thermodynamic laws and its relevance for economics, (ii) behavioral psychology and resulting limitations of individuals’ decision-making under conscious consumer theory, (iii) power theories of political science, and (iv) ethical considerations. The article suggests that ontological and epistemological discrepancies across disciplines, as well as the consequential neglect of several mechanisms have so far limited scientific progress to guide meaningful political action.

Clemens W. Gattringer, Marine Policy, Available online 18 December 2017, In Press

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