Modeling Habitat and Water-Quality Mediated Trophic Interactions in the Chesapeake Bay Food Web

The broad-scale, long-term effects of eutrophication on estuarine fisheries ecosystems are not well understood. Additional nitrogen can enrich system productivity; however, hypoxia resulting from excess nutrients can alter trophic flow.  To explore these potential pathways, we applied habitat volume models based on water quality conditions to two different food web models of the Chesapeake Bay – a simple fisheries ecosystem model based first order species interactions and the Chesapeake Bay Fisheries Ecosystem Model (CBFEM, based in Ecopath with Ecosim).  To estimate the water quality influences, we developed habitat volume models based on 1) water quality model output (i.e., salinity, temperature, and dissolved oxygen) and 2) species tolerances for these water quality parameters.  In the ecosystem models, modeled monthly variability in water quality conditions were used to drive changes in the habitat volumes of the fished species. Monthly habitat volume overlap of predator-prey pairs drove changes in the interaction/consumption rates of both models.  In addition, in the CBFEM, monthly variability in species-specific habitat volume forced species production rates. We explored scenarios with changes in habitat volumes based on high and low nutrient inputs. These scenarios provided some bounds on the likely system-wide impacts of eutrophication.