Relevance of nano- and microplastics for freshwater ecosystems: A critical review

The current paper critically reviews the state-of-the-science on (1) microplastics (MP) types and particle concentrations in freshwater ecosystems, (2) MP and nanoplastics (NP) uptake and tissue translocation, (3) MP/NP-induced effects in freshwater organisms, and (4) capabilities of MP/NP to modulate the toxicity of environmental chemicals. The reviewed literature as well as new data on MP and NP concentrations in the river Elbe and on particle uptake into human cells indicate an environmental relevance of small particles in the low nano- and micrometer range higher than that of larger MP.

Rita Triebskorn, Thomas Braunbeck, Tamara Grummt and al., TrAC Trends in Analytical Chemistry, Volume 110, January 2019, Pages 375-392

The article

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Floating matter: a neglected component of the ecological integrity of rivers

Floating matter (FM) is a pivotal, albeit neglected, element along river corridors contributing to their ecological integrity. FM consists of particulate matter of natural (e.g. wood, branches, leaves, seeds) and anthropogenic (e.g. plastic, human waste) origin as well as of organisms that, due to its properties, is able to float on the water surface. In this paper, we provide a comprehensive overview of the FM cycle and the fundamental environmental functions FM provides along rivers. Indeed, FM serves as an important geomorphological agent, a dispersal vector for animals and plant propagules, a habitat, a resource, and a biogeochemical component. Furthermore, we collected data on the amount of FM accumulating at dams and in reservoirs, and related it to key characteristics of the respective catchments. River fragmentation truncates the natural dynamics of FM through its extraction at damming structures, alteration in the flow regime, and low morphological complexity, which may decrease FM retention. Finally, we identify key knowledge gaps in relation to the role FM plays in supporting river integrity, and briefly discuss FM management strategies.

O. Shumilova, K. Tockner, A. M. Gurnell, S. D. Langhans, M. Righetti, A. Lucía, C. Zarfl, Aquatic Sciences, , 81:25

The article

No evidence of microplastic impacts on consumption or growth of larval Pimephales promelas

Microplastics are an abundant pollutant in aquatic systems, but little is known regarding their effects on larval fish. We conducted foraging and growth experiments to observe how increasing densities of microplastics (polyethylene microspheres) impact the foraging and growth of Pimephales promelas larvae. We found minimal impacts on larval consumption of Artemia nauplii in the consumption study, as well as little impact on total length after 30 d of the growth experiment.

Timothy David Malinich, Nathan Chou, Maria S. Sepúlveda, Tomas O. Höök, Environ Toxicol Chem, 2018, 37:2912–2918. © 2018 SETAC

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Effects of virgin microplastics on goldfish (Carassius auratus)

Microplastics (MPs) are abundant in freshwater and marine environments. They are diverse shape and size and are ingested by organisms. In this study, goldfish (Carassius auratus) were exposed via diet to three types of virgin MPs material types and shapes including fibers, fragments, and pellets. After six weeks of exposure, various sub-lethal effects, but no mortality, was observed. Fish exposed to plastic showed significant weight loss compared with the control. Fibers were found in the gills, gastrointestinal tract (GIT), and feces were not likely to accumulate in the GIT. Pronounced and severe alterations were found in the livers of fish exposed to fibers. The distal intestine showed more pronounced and severe changes compared to the proximal intestine, likely due to an intake of fibers. The ingestion of fibers caused the highest frequencies of progressive and inflammatory changes in the livers and intestines. This is in accordance with the higher organ index in these organs compared to other texa. Conversely, fragments and pellets were not ingested but chewed and expelled. Chewing process resulted in damages to the jaws as ranging from slight exfoliation to deep incisions. The highest frequency of regressive and circulatory (e.g., dilated sinusoids) changes was found in fish exposed to fragments, specifically in the upper and lower jaw, and in lower jaw and liver, respectively. Together, these results demonstrate that ingestion and chewing of MPs lead to damages in various organs and tissues of the gastrointestinal system, and suggest that different materials can have drastically different impacts on fish.

K. Jabeen, B. Li, Q. Chen and al., Chemosphere, Volume 213, December 2018, Pages 323-332

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Microplastics pollution in different aquatic environments and biota: A review of recent studies

Microplastics (MPs) are generated from plastic and have negative impact to our environment due to high level of fragmentation. They can be originated from various sources in different forms such as fragment, fiber, foam and so on. For detection of MPs, many techniques have been developed with different functions such as microscopic observation, density separation, Raman and FTIR analysis. Besides, due to ingestion of MPs by wide range of marine species, research on the effect of this pollution on biota as well as human is vital. Therefore, we comprehensively reviewed the occurrence and distribution of MPs pollution in both marine and freshwater environments, including rivers, lakes and wastewater treatment plants (WWTPs). For future studies, we propose the development of new techniques for sampling MPs in aquatic environments and biota and recommend more research regarding MPs release by WWTPs.

S. Rezania, J. Park, M. F. Md Din and al., Marine Pollution Bulletin, Volume 133, August 2018, Pages 191-208

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The effects of microplastic on freshwater Hydra attenuata feeding, morphology & reproduction

Microplastic pollution has been a growing concern in the aquatic environment for several years. The abundance of microplastics in the environment has invariably led them to interact with a variety of different aquatic species. The small size of microplastics may make them bioavailable to a great range of species however, the impact this may have is not fully understood. Much of the research on microplastic pollution has focused on the marine environment and species with little research undertaken in freshwater. Here we examine the effect of microplastics on the freshwater cnidarian, Hydra attenuata. This study also describes the development and use of a bioassay to investigate the impact of microplastic on freshwater organisms. Hydra attenuata play a vital role in the planktonic make up of slow moving freshwater bodies which they inhabit and are sensitive environmental indicators. Hydra attenuata were exposed to polyethylene flakes (<400 ìm) extracted from facewash at different concentrations (Control, 0.01, 0.02, 0.04, 0.08 g mL−1). The ecologically relevant endpoint of feeding was measured by determining the amount of prey consumed (Artemia salina) after 30 and 60 min. The amount of microplastics ingested was also recorded at 30 min and 60 min. After which Hydra attenuata were transferred to clean media and observed after 3, 24, 48 & 96 h with changes in their morphology and reproduction (Hydranth numbers) recorded. The results of this study show that Hydra attenuata are capable of ingesting microplastics, with several individuals completely filling their gastric cavities. Significant reductions in feeding rates were observed after 30 min in 0.02 & 0.08 g mL−1 and after 60 min in 0.04 & 0.08 g mL−1 exposures. Exposure to the microplastics caused significant changes to the morphology of Hydra attenuata, however these changes were non-lethal. This study demonstrates that freshwater Hydra attenuata is capable of ingesting microplastics and that microplastic can significantly impact the feeding of freshwater organisms.

Fionn Murphy, Brian Quinn, Environmental Pollution, Volume 234, March 2018, Pages 487-494

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Microplastic contamination of river beds significantly reduced by catchment-wide flooding

Microplastic contamination of the oceans is one of the world’s most pressing environmental concerns. The terrestrial component of the global microplastic budget is not well understood because sources, stores and fluxes are poorly quantified. We report catchment-wide patterns of microplastic contamination, classified by type, size and density, in channel bed sediments at 40 sites across urban, suburban and rural river catchments in northwest England. Microplastic contamination was pervasive on all river channel beds. We found multiple urban contamination hotspots with a maximum microplastic concentration of approximately 517,000 particles m−2. After a period of severe flooding in winter 2015/16, all sites were resampled. Microplastic concentrations had fallen at 28 sites and 18 saw a decrease of one order of magnitude. The flooding exported approximately 70% of the microplastic load stored on these river beds (equivalent to 0.85 ± 0.27 tonnes or 43 ± 14 billion particles) and eradicated microbead contamination at 7 sites. We conclude that microplastic contamination is efficiently flushed from river catchments during flooding.

Rachel Hurley, Jamie Woodward, James J. Rothwell, Nature Geoscience,

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