Effects of Microplastics in Sediment Organisms
There is a general assumption that plastics in the oceans to a large extent will end up in sediments. This study aimed to clarify whether the presence of microplastics will affect the species composition and sediment-dwelling organisms at different trophic levels. The experiment was conducted using 24 mesocosms with sediment collected in the outer Oslofjord.   Continuous water supply and air pumps were supplied to each mesocosm throughout stabilization and exposures. The mesocosms were divided in four treatment groups and dosed with 1 µm and 6 µm fluorescent polystyrene beads, as well as beach plastics from the Adriatic Sea (100-200 µm).   Following termination, sediment core samples were taken for microfauna and meiofauna analysis. The remaining sediment in the boxes was sieved in cold seawater to extract all visible organisms. Samples were kept at 2oC to keep them alive until further analysis, and the sediment for barcoding were kept in freezer (-80oC).   Bacterial eDNA was extracted for DNA metabarcoding from these sediments to analyze possible differences in species composition due the different treatments. For meiofaunal community, both eDNA the more time sensitive eRNA extraction will be employed to ensure analysis of DNA of only live meiofauna at the time of termination.