[Bacteriological detection of crude oil contamination in the Bahía Blanca estuary]

In order to evaluate the distribution of occasional oil spills produced by floating system for transferring crude oil, the number of hydrocarbon-degrading bacteria was counted in superficial sediments from Bahía Blanca Estuary, using the Most Probable Number method. Sediment were collected from ten stations located between buoys 21 and 16. Heterotrophic aerobic marine bacteria were counted on Marine Agar 2216. Determination of organic carbon was also carried out. On the base of the number of hydrocarbon-degrading bacteria, statistical analysis differentiated two zones with different degree of pollution, one including the stations of the Principal Channel, with average values, expressed as log10, which ranged from 2.98 to 3.65 bacteria/g of dry sediment, and the other from 4.16 to 4.37, located in small channels on the Southern coast. These results suggest a drift of the oil perpendicular to the Principal Channel, probably caused by the action of predominant winds with direction N, NNW. A linear regression analysis determined highly significant relationship between organic carbon and both bacterial groups. This study shows that the spilled oil is affecting productive zones of the estuary.