Abstract
Steadily increasing inputs of microplastics pose a growing threat to aquatic fauna, but laboratory studies potentially lack realism to properly investigate its effects on populations and ecosystems. Our study investigates the trophic and ontogenetic transfer of microplastics in a near-natural exposure scenario. The controlled outdoor freshwater mesocosms were exposed to polyamide (PA) 5–50 µm in size in concentrations of 15 and 150 mg L−1 and a control without microplastic addition. To verify the uptake of particles via the food chain, larvae and imagines of the midges Chaoborus crystallinus and C. obscuripes were examined, which feed on zooplankton during their larval stage. Larvae were captured after 117 days and imagines were caught in emergence traps that were emptied weekly. To detect the microparticles within the organisms, 200 larvae and 100 imagines per application were macerated and treated with fluorescent dye before investigation under a fluorescent microscope. We could detect up to 12 PA particles per individual larvae, while nearly no plastic was found in the imagines. This shows that, while Chaoborus sp. takes up microplastics via predation, most of the pollutant is egested through regurgitation and remains in the water, where it can further accumulate and potentially harm other organisms.
Highlights
Academic Editor: Kai ZhangMicroplastic pollution is a potential threat to our waters and has attracted increased public and scientific attention in recent years [1,2]
The most common polymer types reported in freshwaters are polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), polyamide (PA) has been frequently detected in aquatic ecosystems and biota but received disproportionally low attention in previous studies [8]
The advantage of mesocosms over laboratory experiments is that a realistic exposure scenario of pollutants can be created and interactions between trophic levels can be enabled and observed [43]
Summary
Microplastic pollution is a potential threat to our waters and has attracted increased public and scientific attention in recent years [1,2]. Since most plastic contamination originates from land-based sources, such as sewage, industry, or roads [3], freshwater ecosystems are exposed to high plastic intakes annually [4]. It is evident that high amounts of plastic debris enter our freshwater ecosystems [4] and while rivers carry 2.4 million tons of plastic into the oceans annually [7], a large fraction remains in rivers and lakes, where it potentially harms aquatic biota. The most common polymer types reported in freshwaters are polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), polyamide (PA) has been frequently detected in aquatic ecosystems and biota but received disproportionally low attention in previous studies [8]
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