Studies on the Impact of Sewage-Associated Microorganisms on Indigenous Seal and Bacterial Populations and Drinking Water Quality at McMurdo Station

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McMurdo Station, Antarctica, has been releasing macerated, untreated human sewage into the pristine marine waters off the coast for years. The marine waters impacted by the sewage plume sometimes extend to the drinking water intake at Intake Jetty. Additionally, deposit feeding invertebrates located within the area impacted by the sewage effluents have been show to not only assimilate the nutrients associated with the sewage but also exhibit increased mean body and organ sizes. A previous study found preliminary, but inconclusive, evidence that the sewage-associated bacterium, clostridium perfringens, was colonizing Weddell seals feeding in the impacted area. It is hypothesized that (!) Weddell seals are being colonized by sewage -associated bacteria and viruses, (2) sewage-associated bacteria are exchanging their DNA with indigenous species, potentially altering the procaryotic gene pool of this ecosystem (3) sewage-associated bacteria and viruses are entering the drinking water system at McMurdo Station and (4) the current methods used to monitor the microbiological quality of marine and drinking waters at McMurdo Station are underestimating the risks associated with their respective contact and/or ingestion. These hypotheses will be addressed by using molecular techniques (e.g., pulse field gel electrophoresis, PCR), in situ microcosms for gene transfer experiments, more sensitive culture based techniques for determining the extent of sewage contamination in marine waters, sediments and seal feces and scat and performing the most extensive microbiological survey of the drinking water distribution system to date. A major focus of this work will be determining if the same C. perfringens genotypes that are present in the sewage are related to those isolated from seal feces and scat, marine waters and sediments and drinking water samples. This approach has been used in other systems to establish a direct epidemiological link between a bacterium's source and the colonized (infected) host. In general, the results from this study will provide information which can be used in the monitoring and design of remediation efforts of coastal waters off of McMurdo Station and other coastal waters around Antarctica that are being impacted by the discharge of untreated human sewage. The data will also be as a baseline for studies of ecosystem recovery following the planned installation of a sewage treatment plant at McMurdo Station.