Food web structure of fouling communities along a depth gradient: a North Sea case study

Man-made structures offer habitat for sessile macrofauna and thus alter the natural biodiversity. This alteration has an impact not only on ecosystem structure, but also on ecological functioning, e.g. food web interactions. Trophic linkages among organisms are a fundamental requirement to explaining energy flow from primary carbon fixation to higher trophic level consumers and hence to explaining how man-made structures impact ecosystem functioning. The aim of this study is to disentangle trophic interactions within fouling communities at different depths of artificial hard substrates that are present in the Belgian part of the North Sea. Fouling organisms were collected along the entire depth gradient (from the intertidal zone down to the erosion protection layer) of a gravity-based windmill. Additionally, food sources, such as plankton, and mobile predators were sampled from the surrounding water column. All organisms were identified to the lowest possible taxonomic level and were processed for stable isotope analysis (δ15Ν and δ13C) to explore their trophic niche. This study reveals differences in food web structure to be aligned with the species richness turn across depths. The anticipated results will divulge the unique trophic linkages among hard substrate organisms opposed to the natural trophic interactions of soft substrate species in the North Sea. Disentangling trophic linkages between species, providing an idealized picture of the trophic patterns in the ecosystem is crucial to the understanding of marine food webs. This study hence provides fundamental insights into the functional effects of proliferating artificial hard substrates in marine ecosystems.

Abstract of an Oral Presentation or a Poster