Effects of polyethylene microplastics on benthic invertebrates and ecosystem function in lotic mesocosms

, Silva Carlos, Machado Ana Luísa, Campos Diana, Rodrigues Andreia, Patrício Silva Ana L., Gravato Carlos, Pestana João L.t..

Given the ubiquitous presence of microplastics (MPs) in freshwaters and their concerning levels in riverbeds, it is of utmost importance to gather ecotoxicological data on macroinvertebrate community and ecosystem functioning. Using indoor artificial streams, this study evaluated the effects of polyethylene microplastics (PE-MPs, one of the most common polymers found in freshwaters; concentration range: 0.1 – 1 – 10 g/kg) on macroinvertebrate benthic community and ecosystem functioning (using primary production and leaf decomposition - as functional endpoints ) after 10 days of exposure. Plus, MP internal concentration was assessed for several invertebrates. The presence of PE-MPs in freshwater sediments altered the macroinvertebrate community structure, namely by the reduction in the abundance of grazers and fine sediment eaters such as Chironomus, Baetis and Ephemerella. Such reduction can be related to the ingestion of MPs, which was higher on these functional feeding groups (i.e., grazers and collectors). There were no alterations on the functional parameters analyzed, primary production and leaf decomposition. Results show that invertebrates' feeding strategies are the main drivers for MPs ingestion and effects. The absence of changes in primary production and leaf decomposition might be related to functional redundancy within invertebrate communities under short-exposure assays. Determination of MP after 10 days of exposure confirms ingestion by several benthic invertebrates highlighting the potential deleterious ecological effects of microplastics to freshwater and nearby terrestrial ecosystems. Thanks are due to FCT/MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020, through national funds) and the research project ComPET (POCI-01-0145-FEDER-030361, funded by FEDER, through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (OE)).

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