Trophic Mass-Balance Model of Alaska's Prince William Sound Ecosystem, for the Post-Spill Period 1994-1996
A better understanding of the whole Prince William Sound (PWS) food web and its dynamics was achieved by constructing a balanced trophic model using the Ecopath approach. The PWS model was a cohesive synthesis of the overall biotic community with a focus on energy flow structure, and response to perturbations, both natural and anthropogenic. Forty-eight biotic components were included in the PWS model ranging from life stages of individual species to aggregated functional groups. These groups were organized into primary producers, zooplankton, benthic invertebrates, planktivorous "forage fishes", larger fishes, birds, mammals, and detritus, for the purpose of model documentation. Estimates of biomass flows related to fisheries landings and discards in Prince William Sound were also incorporated. Outputs of the Ecopath model included biomass and flux estimates for individual groups that were refined through the collaborative mass-balancing approach, and useful characterizations of the whole food web. The outputs of Ecosim and Ecospace, which include simulations of population trajectories through time, and habitat-based re-distributions of organisms in space, were also featured. The Ecopath model of PWS could be used to help guide future research programs in the region, to help assess impacts of the EVOS, and to help resource agencies and local communities achieve ecosystem-based conservation and management in the face of increasing human activities in the region. This approach could also be used to help distinguish the relative importance of physical forces and tropic forces in marine ecosystems.
