Comparison of the Trophic Structure of two Benthic Communities in the German Bight

Jennifer.Dannheim [ at ]


A sound knowledge on trophic interactions is essential to understand ecosystems and their resilience to anthropogenic perturbations. Stable isotope analysis (carbon and nitrogen) and literature information on taxon-specific prey spectra were combined to explore the food web structure of two major benthic assemblages in the German Bight (southern North Sea): the Amphiura filiformis-association of silty sands, and the Tellina fabula-association of fine sands. Carbon isotopic signatures of suspended particulate and sediment organic matter were consistent with ranges reported for temperate marine phytoplankton, suggesting that both food webs are mainly fueled by pelagic primary production. More negative δ13C values at the Amphiura filiformis-station furthermore indicated a small contribution of continental organic matter at this station, which is located off the Weser and Elbe estuaries. Primary consumer feeding guild composition varied between assemblages, reflecting differences in physical properties of sediments and food availability: deposit- and interface feeders were the most important primary consumer guilds in the Amphiura filiformis-association, whereas filter- and interface feeders played a major role in the Tellina fabula-association. Both communities had four trophic levels, with fishes and predatory polychaetes occupying the highest trophic positions. While primary consumer guilds occupied the same trophic level in the Amphiura filiformis-association, deposit feeders of the Tellina fabula-association had a trophic level intermediate of other primary and higher order consumer guilds, likely due to differences in species composition and selective feeding. Both food webs were characterized by their high directed connectance, trophic generalism of consumers, and a large proportion of cannibalistic taxa. These features are characteristic of marine food webs in general, but also reflect a selection for opportunistic taxa in the southern North Sea, a region characterized by high levels of environmental and anthropogenic disturbances.

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Steger, J. (2016): Comparison of the Trophic Structure of two Benthic Communities in the German Bight , Master thesis, Universität Bremen, Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung.

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