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Microplastic loads in Eurasian otter (Lutra lutra) feces—targeting a standardized protocol and first results from an alpine stream, the River Inn
Summary
Researchers developed a standardized method for extracting and analyzing microplastics from Eurasian otter feces to use these apex predators as indicators of aquatic pollution. Testing the method on 50 samples from Austria's River Inn, they found microplastics of various sizes and types, including fibers and tire wear particles, in every sample. The study suggests that otters can serve as effective bioindicators for tracking microplastic contamination in river ecosystems.
Microplastics (MP) are omnipresent in a wide range of environments, constituting a potential threat for aquatic and terrestrial wildlife. Effects in consumers range from physical injuries to pathological reactions. Due to potential bioaccumulation of MP, predators are of particular concern for MP induced health effects. The Eurasian otter is an apex predator in (semi-)aquatic habitats feeding primarily on fish. Furthermore, the species is classified as "near threatened" on the IUCN Red List. Thus, the Eurasian otter is of conservation concern and may serve as a bioindicator for MP pollution. Feces can be used to detect pollutants, including MP. Initial studies confirmed the presence of MP in otter feces (= spraints). However, as specific, validated protocols targeting at an efficient and standardized extraction of MP from otter spraints are missing, experimental results reported from different groups are challenging to compare. Therefore, we (i) present steps towards a standardized protocol for the extraction of MP from otter feces, (ii) give recommendations for field sample collection of otter spraints, and (iii) provide a user-friendly step-by-step workflow for MP extraction and analysis. Applying this framework to field samples from five study sites along the River Inn (n = 50), we detected MP of different sizes and shapes (ranging from microfibers to road abrasion and tire wear) in all otter spraint samples.