A Quantitative Food Web Model for the Macroinvertebrate Community of a Northern German Lowland Stream

Abstract

AbstractTrophic interactions and cycling of organic carbon within the macroinvertebrate community of a Northern German lowland stream were analyzed based on a compartment model. The network model describes the structure of the food web quantifying biomass, production, and consumption of their elements, of the entire system and between trophic levels. System primary production is 153.7 g C m−2 yr−1 and invertebrate production 53.3 g C m−2 yr−1. Invertebrate consumption amounts to 702.6 g C m−2 yr−1. Main flows are identified between trophic level 1 and 2 and are connected with highly productive compartments. ‘Anodonta and Pseudanodonta’ and Dreissena polymorpha show the highest consumption of all groups with 269.9 g C m−2 yr−1 and 114.1 g C m−2 yr−1, respectively. System consumption is highest on the import from the upstream lake with 532.5 g C m−2 yr−1, sediment detritus with 135.5 g C m−2 yr−1, and primary producers with 25.7 g C m−2 yr−1. The lowest predation pressure is observed for Bivalvia with an ecotrophic efficiency of <10% and highest for Chironomidae with 91%. Approximately 20% of organic matter entering the detritus pool are recycled to the living groups of the system. Transfer efficiencies between discrete trophic levels are generally low except for transfer of detrital material between level I and II.