Abstract The population of the United States Antarctic Program at McMurdo Station is approximately one thousand people in the austral summer. Untreated sewage is disposed through a macerator and released into the marine environment as effluent directly offshore of the station at the twenty meter depth contour. Although the Principal Investigators have previously mapped the boundaries of the sewage effluent plume in the water column, the degree to which anthropogenic sources of organic enrichment is taken up and passed through the antarctic benthic food web is unknown. Coincidentally, the foundation for understanding of the structure, composition and functioning of antarctic benthic communities comes primarily from field research conducted within the boundaries of the McMurdo sewage outfall plume. The purpose of this research is to determine if sewage-derived organic material is assimilated by the benthic food web and its extent of influence and if there is a biological response to anthropogenic organic enrichment and how this compares to natural organic enrichment by seals. This research will provide an understanding of the relative contribution to natural organic enrichment by seals. A secondary purpose will be to understand the relative contribution of different organic sources to the benthos and the way that this material moves through the food web. The Principal Investigators will use stable carbon, sulfur, and nitrogen isotope ratios and fecal-derived bacteria as indices and compare the influence of sewage and seal-derived organic matter with natural organic sources from the under-ice, benthos, and water column. They will test the hypothesis that sewage influence is greater than previously thought. This understanding is essential for effective station sewage management and policy decisions and for the design and interpretation of polar benthic research conducted in the vicinity of human inhabitation or other sources of organic enrichment.
