Sylt is the largest North Frisian island. It stretches from north to south near to the North Sea coast of Schleswig Holstein, Germany. The island is famous for it’s distinctive shape and shoreline. The 40 km long sandy beach is well known for it’s tourist resorts. Our focus lies on an intertidal sandflat in Könighafen, a tidal embayment at the northern end of the island Sylt (55°02’N;8°26’E). For studying the biogeographical patterns of organisms it is essential to compare the composition of communities with respect to biotic and abiotic environmental factors. The lugworm Arenicola marina strongly bioturbates considerably parts of the tidal flats in the German Wadden Sea. Surveys could demonstrate that their burrow and feeding activities disturb or even inhibit some macrobenthic primarily sedentary species. To achieve reliable patterns, microbial organisms hailing from the sediment, such as protists, have to be taken into account, too. They play fundamental roles in energy flow and elemental cycling in aquatic ecosystems. The experiment comprises different blocks each of which consists of a plot in its natural state (ambient plot) and an exclusion plot, where 1-mm meshed net was inserted in 10 cm depth to exclude the lugworm and thus to prevent bioturbation. Samples for our study where derived from three different blocks in the mid intertidal zone each containing subsamples from the exclusion plots and the ambient plots.