Open Access

The achievement and monitoring of a good environmental status on continental shelf seas requires the use of acoustic remote sensing techniques due to their range. The interpretation of acoustic signals for the identification of benthic communities, however, is still in its infancy. In this thesis, the results of two field campaigns conducted in a sandy environment off the shore of Sylt Island (North Sea) utilizing ship- and lander-based acoustic and optical remote sensing techniques are discussed. The objective of the thesis is a better knowledge of the impact of the polychaete Lanice conchilega on physical seafloor properties, especially roughness at a cm to mm scale, which is relevant for understanding acoustic scatter. The results show a clear impact of L. conchilega on roughness even in sparse populations of less than 2% coverage. However, these sparsely populated areas could not be reliably identified with acoustic data; a denser population of L. conchilega provided a clearer signal for the acoustic remote sensing methods. The results are promising regarding the broader use of acoustic remote sensing techniques for environmental monitoring in selected habitats, although the determination of minimum population thresholds that can be identified will require further studies.