Projecting environmental and krill fishery impacts on the Antarctic Peninsula food web in 2100

Abstract

The Antarctic Peninsula ecosystem is extremely sensitive to climatic variability and other anthropogenic perturbances ascribed to biomass extraction by fisheries. An Ecopath with Ecosim model calibrated for the 1996–2012 period was projected into the future (2100) under three different climate projections for environmental variables (sea ice extent, open water area and chlorophyll-a concentration) and three Antarctic krill fishery scenarios (no-take, constant and decadal increase until doubling of the current catches). The relative impact of different drivers controlling Antarctic food web dynamics was evaluated with a sensitivity analysis and the temporal variability of several functional group and ecosystem indicators. Under these scenarios, environmental variability resulted in a greater impact on the Antarctic food web in 2100 projections compared with the krill fishery. Chlorophyll-a biomass strongly influenced the temporal variability of functional groups, suggesting predominant bottom-up control on the food web. An alternative food web structure was observed in 2100, with a marked decline in krill population biomass (from<50% to near extinction depending on the environmental projection) and an increase in salps and other zooplankton groups. A reduction in the biomass of sea ice and krill-dependent predators, such as Adélie and chinstrap penguins and crabeater seals, was also observed. The absence of functions modelling the spatial and seasonal variability of the krill fishery might cause an underestimation of its ecosystem impacts. This work provides useful insights into the dynamic responses of the Antarctic food web under likely environmental projections and highlights critical points that need to be addressed to improve the understanding and parametrization of the Antarctic food web to anticipate future variability.