To understand and project how marine ecosystems will respond to changing climate conditions and direct human impacts such as fisheries requires integrated ecosystem analyses at scales previously unexplored. Analyses of Southern Ocean ecosystems are no exception. Despite maintaining unique biological diversity there has been more than two centuries of exploitation of living resources, the region is experiencing rapid changes in ocean temperature and seasonal ice cover, and showing significant changes at all trophic levels. However, complex interactions within food webs modify responses of individual species and influence the response of entire ecosystems to change. To make reliable projections of the impacts of past and future change on Antarctic ecosystems first requires a fundamental understanding of the factors that determine both the structure and function of the food webs at multiple scales. The ocean ecosystems around the west Antarctic Peninsula and South Georgia provide a useful basis for developing comparative analyses of Antarctic ocean ecosystems. There are clear and expected differences in seasonality and species composition between the two ecosystems, but these mask an underlying similarity in ecosystem structure and function. This similarity results from the two ecosystems being part of a continuum, from more ice-covered regions in the south to open water regions in the north. Within this continuum the major factors affecting ecosystem structure and function are the sea ice, the biogeochemical conditions and the connectivity generated by the flow of the Antarctic Circumpolar Current. The similarity of structure and strong connectivy mean that the projections of future change will require generic models of these ecosystems that can encompass changes in structure and function within a connected continuum from ice-covered to open water in winter.

Eileen Hofmann's research interests are in the areas of physical-biological interactions in marine ecosystems, climate control of diseases in marine shellfish populations, descriptive physical oceanography, and mathematical modeling of marine ecosystems. She has worked in a variety of marine environments, most recently the continental shelf region off the western Antarctic Peninsula. She is participating in the Integrating Climate and Ecosystem Dynamics in the Southern Ocean Program, which is an international multidisciplinary program focused on understanding linkages between food webs, biogeochemical cycles and climate.

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