This project supports the analysis of marine benthic samples collected in the vicinity of Arthur Harbor, Antarctica, following an oil spill that resulted from the grounding of the Argentine supply ship Bahia Paraiso. The vessel grounded on January 28, 1989, and spilled an estimated 170,000 gallons of diesel and aviation fuel, which contaminated shorelines located up to 15 miles from the site of the accident. Although small in size, this spill is of significance because the affected areas include sites that are used extensively for fundamental scientific research and are composed of highly rich and productive assemblages of marine flora and fauna, which might include components that are very sensitive to unusual anthropogenic disturbances. The experimental design includes tests for possible oil-spill effects on these various components of the intertidal and subtidal communities. In addition, a great deal of importance is placed on basic research approaches to provide detailed descriptions of the structure and composition of these communities and to determine the role of natural environmental factors (e.g., depth, sediment type, organic input, environmental stability) in controlling patterns of spatial distribution and long-term variability (for those components having an historical data base). These studies will provide an empirical assessment of possible effects of the Bahia Paraiso oil spill on benthic components of the Arthur Harbor region. In addition, data from these studies will be extremely important in providing a basis for a more comprehensive understanding of the natural structure and dynamics of the Arthur Harbor benthic ecosystem, as well as a basis for comparison of the benthos with other marine ecosystems of the world. Finally, these analyses will provide baseline data to support continued studies of long-term, natural and man-induced variation in important living components of this diverse and productive region.