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Effects of two types of microplastics (car tire abrasion and polystyrene) on earthworms Eisenia andrei on multiple levels of biological organization

Microplastics are small plastic fragments of sizes less than 5 mm, which are widely distributed in marine and terrestrial environments. Due to their key role in soil ecosystem, earthworms are often used as model organism in soil ecotoxicology. Therefore, the aim of this study was to evaluate effects of two most common types of microplastics on earthworms Eisenia andrei. Tested microplastics included car tire abrasion and polystyrene in concentrations 1 mg/kg and 1000 mg/kg, and 0.1 mg/kg and 100 mg/kg respectively. The study was conducted by exposing earthworms to microplastics in natural soil for 2, 7, 14 and 28 days. Acute toxicity for these exposure times as well as avoidance behaviour after 48 h were evaluated. Further investigation included various biomarkers and subcellular endpoints, namely, carboxylesterase (CES), acetylcholinesterase (AChE), glutathione S-transferase (GST), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione (GSH) and reactive oxygen species (ROS) fluorescence and multixenobiotic resistance activity (MXR). Since no mortality was observed, same concentrations were chosen for all tested endpoints. Effects on subcellular level of both microplastics could be observed, all regarding the oxidative stress indicators (e.g., ROS and GSH fluorescence, CAT, GPx and GR activity). Reproduction tests showed lower production of cocoons and juveniles compared to control. Observed changes indicate the potential negative effect of microplastics to soil organisms. These findings provide a new insight regarding the toxicological effects of microplastics on earthworm as a key organism of terrestrial ecosystems.

microplastics ; biomarkers ; multixenobiotic resistance activity ; oxidative stress ; reproduction

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