Analysing long-term change in small benthos: Geomorphological dynamics affects method selection

Abstract

In the tidal inlets of the northern Wadden Sea, species composition of selected taxa of the small benthos is compared to a study performed some 35 years before, using the same methods and sampling the same sites. Site-by-site comparisons suggest a dramatic change in community composition at a local scale. However, geomorphology is highly dynamic in this area, and sediment composition, water depth, or both, had changed during the intermediate decades in most of the sites. Since most of the species are limited to a single sediment type, a habitat approach was used for an alternative analysis of the data. This contradicted the idea of dramatic change but revealed relatively high stability of species composition at a regional scale, indicating that local change cannot be up-scaled to larger areas in this highly dynamic environment. Instead, a habitat approach is more adequate though increasing environmental dynamics requires increasing sampling effort. As a by-product of this study, 8 new taxa of Platyhelminthes are described: Karlingia septentrionalis n. sp., Paracalviria diadema n. sp., Kataplana macrobursalia n. sp., Adenorhynchus compositus n. sp., Litucivis simplex n. sp., Scoliopharyngea magnaspina n. sp., Promesostoma convolutum n. sp., and Gnathorhynchus rostellatus indivisus n. spp.