MEPS 569:37-54 (2017)  -  DOI: https://doi.org/10.3354/meps12100

ABSTRACT: Under climate change, alterations in primary production and concomitant changes in community dynamics are expected in many marine ecosystems. We used an Ecopath with Ecosim (EwE) marine ecosystem model of the western Antarctic Peninsula to simulate effects on the food web based on proposed changes in the primary production regime expected as a result of climate change. Scenarios for trophic modeling are based on published results from coupled high-resolution regional ocean sea-ice and ice-shelf models, which consider alterations in water circulation from westerly wind intensification, increases in circumpolar deep water upwelling, iron upwelling, and decreases in sea-ice extent. Modeling scenarios included 6, 15, and 41% increases in phytoplankton production with equivalent percentage decreases in ice algal production, and 1 scenario with 15% increase for phytoplankton with no change for ice algae. These scenarios were achieved through linear forcing functions within the EwE software. We framed ecosystem changes in terms of biomass, species diversity, mean trophic level, trophodynamics, and network metrics. Simulations revealed that in each scenario, mean trophic level increased, species diversity generally decreased, and energetic pathways were reorganized. Modeled changes in the planktonic invertebrate assemblage include changes in 2 key competitors, krill and salps. For example, model results predict declines in krill biomass with concomitant increases in salp biomass. In all scenarios that assumed a negative change in ice-algae production rates due to sea-ice habitat loss, whale, seal, and penguin populations were negatively affected. Changes in ecosystem structure in this sensitive region may serve as an indicator of changes expected in the Southern Ocean.

KEY WORDS: Antarctic warming · Trophodynamics · Climate change · Antarctic Peninsula · Ecosystem model · Ecopath with Ecosim