The annual advance and retreat of pack ice may be the major physical determinant of spatial and temporal changes in the structure and function of antarctic marine communities. Interannual cycles and/or trends in the annual extent of pack ice may also have significant effects on all levels of the food web, from total annual primary production to breeding success in seabirds. Historical records indicate a six to eight year cycle in the maximum extent of pack ice in the winter. During this decade, winters were colder in 1980 and 1981, and again in 1986 and 1987. Winter-over survival in Adelie penguins varied on the same cycle, higher in winters with heavy pack ice. This Long Term Ecological Research (LTER) project will define ecological processes linking the extent of annual pack ice with the biological dynamics of different trophic levels within antarctic marine communities. The general focus is on interannual variability in representative populations from the antarctic marine food web and on mechanistic linkages that control the observed variability in order to develop broader generalizations applicable to other large marine environments. To achieve these objectives, data from several spatial and temporal scales, including remote sensing, a field approach that includes an annual monitoring program, a series of process-oriented research cruises, and a modeling effort to provide linkages on multiple spatial and temporal scales between biological and environmental components of the ecosystem will be employed.
