Abstract
As documented by the numerous publications that have appeared in recent years, plastic pollution of the environment and the effects on the respective ecosystems are currently one of the most intensely discussed issues in environmental science and in society at large. Of special concern are the effects of micro- and nano-sized plastics. A key issue in understanding the fate and potential effects of micro- and nano-sized plastics is their dynamic nature, as the size, shape, and charge of the particles change over time. Moreover, due to various biological processes, such as the aggregation of organic material and/or bacteria (“biofouling”), the density of plastic particles that settle in the sediments of aquatic ecosystems may be several orders of magnitudes higher than that in the surrounding waters. Consequently, the risk posed by plastic pollution to benthic fauna is considerably high. Nonetheless, the vast majority of studies examining the effects of microplastics have focused on pelagic organisms so far. We therefore conducted a comprehensive literature review to examine the impact of micro- and nano-sized plastics on benthic invertebrates, including the physical and chemical effects of leaching and the interactions of plastic particles with contaminants. Overall, 330 papers were reviewed for their fulfilment of different criteria (e.g. test species, plastic material, particle shape, particle size, exposure concentration, exposure route, assay type, assay duration), with 49 publications finally included in our survey. A comprehensive gap-analysis on the effects of plastic particles on benthic invertebrates, revealed a wide variety of effects triggered by micro- and/or nano-sized plastics but also distinct differences regarding the plastic materials tested, the size fractions applied, the shape of the respective particles and the exposure routes tested. Our review concludes with a discussion of the important research gaps concerning freshwater ecosystems and recommendations for future areas of research.
Highlights
The pollution of aquatic ecosystems with plastic debris is regarded as one of the most serious environmental issues worldwide
The mechanical hazards posed by the ingestion of microand nano-sized plastic particles by organisms in freshwater ecosystems were evaluated in 26 experiments reported in 10 publications (Table 1)
The vast majority (69%, n = 18) of the freshwater investigations examined the physical effects of microplastic fragments, i.e., non-uniform, irregularly shaped particles, and powders (Figure 2C)
Summary
The pollution of aquatic ecosystems with plastic debris is regarded as one of the most serious environmental issues worldwide. Small-sized particles have received increasing attention and are recently of particular concern (e.g., Thompson et al, 2004; Eerkes-Medrano et al, 2015; Rochman et al, 2016) These particles, termed nano- and microplastics, are generally defined by their largest dimensions of 0.001–0.1 μm and 0.1 μm−5 mm, respectively (e.g., Thompson et al, 2004; Moore, 2008) and are both major contributors to plastic pollution in marine as well as freshwater ecosystems (e.g., Thompson et al, 2004; Cole and Galloway, 2015; Chae and An, 2017). The vast majority of studies examining the ecotoxicological effects of nano- and microplastics have focused on pelagic rather than benthic organisms so far
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