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Microplastics occur in marine habitats worldwide. They have been reported from locations as remote and pristine as the Arctic and Antarctic, beyond organisms of several trophic levels. Microplastic ingestion in animals can either happens intentionally or by accident. The microplastic size plays an important role in ingestion as it may correspond to the preferred prey size of predator species. Besides, microplastic transfer and accumulation within the trophic food web are considered as a main factor of plastic exposure in apex species like marine mammals. This study investigated samples of faeces and gastrointestinal tracts of 21 cetaceans stranded along the German North Sea and Baltic Sea coasts between 2016 and 2021. This includes the big stranding event of bachelor sperm whales in 2016 (N = 13) in the North Sea, but also other toothed whale species as well as four baleen whales. All samples were processed after an established cleaning protocol using a conventional washing machine, followed by Nile Red staining and fluorescence microscopy. The subsequent µFTIR spectroscopy of suspected anthropogenic particles then identified microplastic polymer types. A variety of polymer types of the isolated particles could be revealed (e.g., Polyester, Polyolefine, Polyamide, and Polyethylene). Also see: https://micro2022.sciencesconf.org/427077/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

The results from the various investigations and monitoring programmes presented in this report demonstrate the continuous and widespread occurrence of litter in the Wadden Sea and adjacent offshore waters. Marine litter of different sizes and from diverse sources occurs on dunes and beaches, in and on inter- to subtidal sediments and in marine organisms, including protected seabirds and mammals. The OSPAR Beach Litter Monitoring and Monitoring on Litter in Fulmars’ Stomachs provide an evaluation of the temporal development of litter abundance in the southern North Sea. Both programmes clearly show that litter densities have not declined since the last Wadden Sea QSR in 2009, indicating that large amounts of litter are still entering the marine environment either directly within the Wadden Sea or from adjacent waters. The amount of litter entering the marine environment is continuously increasing(Jambeck et al., 2015). This increase is, however, not apparent in the results of the two monitoring programmes. Litter degrades in the marine environment and breaks down into ever smaller fragments. The fragmentation of plastic objects produces microplastics, which are not sufficiently assessed by current monitoring programmes. Densities of microplastics are expected to increase substantially in the future in all marine habitats. Accordingly, scientifically sound monitoring of these synthetic particles with standardized methods that allow for the comparison of results from different programmes will be indispensable.Marine litter is not restricted to specific habitats but occurs in all compartments of the marine environment with a constant exchange between them. Accordingly, monitoring litter densities in both coastal and offshore habitats is essential for a sound evaluation of litter pollution of the Wadden Sea. Many of the investigations presented in this report are on-off events, which do not provide information on temporal trends. However, they do demonstrate that the Wadden Sea is contaminated with marine litter and that litter densities in the Wadden Sea are not lower than in other coastal regions. The litter densities presented in this report provide a valuable baseline for future evaluations of temporal trends. The monitoring of litter in fulmars’ stomachs and the examinations of carcasses of harbour porpoise, harbour seals and eider ducks revealed that litter does not simply occur in the marine environment but actually interacts in a potentially harmful way with the marine biota. It is well established that the ingestion of litter can have deleterious and often lethal effects on marine organisms. It is yet unknown whether marine litter has demographically relevant implications for marine species. For evaluating this, the effects of marine litter must not be considered in isolation but always together with the effects of other environmental stressors such as ocean warming and acidification, eutrophication and the exploitation of natural stocks (see reports on climate change, geomorphology, eutrophication and fisheries). SeveralWadden Sea Plan targets are compromised by the continuous pollution of the North Sea with marine litter. A proper management of the marine litter problem will require appropriate reduction measures and extended and optimized monitoring programmes in order to evaluate future developments.

30 sperm whales (Physeter macrocephalus) stranded along the coasts of the North Sea between January and February 2016. The gastro-intestinal tracts of 22 of the carcasses were investigated. Marine debris including netting, ropes, foils, packaging material and a part of a car were found in nine of the 22 individuals. Here we provide details about the findings and consequences for the animals. While none of the items was responsible for the death of the animal, the findings demonstrate the high level of exposure to marine debris and associated risks for large predators, such as the sperm whale.