Handle with Care—Microplastic Particles in Intestine Samples of Seals from German Waters

The Marine Strategy Framework Directive (MSFD) aims to reduce the marine debris burden in the marine environment by 2020. This requires an assessment of the actual situation, which includes the occurrence as well as the caused impacts. Information on both is scarce when it comes to top predators like marine mammals and the burden of microplastic. This is hampered by the limited access to free ranging marine mammals for collecting samples, as well as sample handling. The present study investigated gastrointestinal tracts and faecal samples of harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) regularly occurring in the German North Sea and Baltic Sea with the aim of gaining information on the occurrence of microplastics. In total, 255 particles ≥100 µm (70 fibres, 185 fragments) were found in exemplary ten intestine and nine faecal samples. The findings ranged from zero fibres and six fragments, up to 35 fibres and 55 fragments per sample. Additionally, this study established a protocol for sample handling, microplastic isolation (≥100 µm) and quantification of gastrointestinal tracts and faecal samples of marine mammals with a low share of contamination. This approach helps to quantify the presence of microplastics in free-ranging marine mammals and is therefore applicable to assess the real burden of microplastic presence in the marine environment.