Ecossa focuses on ecological and ecotoxicological assessment of sediments and soils, using infaunal organisms with special emphasis on Meiofauna (~50-500 µm). This size class in-cludes organisms that are very important for the energy- and carbon flux in benthic habitats. They occur in high abundances, are very species rich and most organisms spend their whole life cycle in the sediment or soil. In most habitats, nematodes are the dominant organism group (80 % of all metazoan organisms on this planet are nematodes!). Except for the pela-gial, they occur in any type of ecosystem. For these reasons, meiofauna and especially nema-todes are very suitable organisms for the assessment of sediments and soils.