Benthic studies of the northwest African upwelling region: psychrophilic and psychrotrophic bacterial communities from areas with different upwelling intensities

Distinct bacterial communities were found in the sediments of the northwest African upwelling area at 17 and 21°N compared to an area with low upwelling intensities at 29 and 35°N. The bacterial community of the central upwelling area at 17/21°N consisted of approximately equal proportions of Gram-negative strains belonging mainly to the genera Alteromonas and Vibrio; most of them were psychrophiles. This could be due to the upwelling of cold water masses in this region, where sediment temperatures were on average 2°C lower than in the northern part of this upwelling area. Here, Gram-positive psychrotrophic Bacillus strains predominated, tolerating growth temperatures higher than 24 °C. A high proportion of these Bacillus strains fermented various carbohydrates and sugar alcohols and utilized citrate as sole source of carbon and energy. In contrast, the abilities to utilize some glycosides, starch, chitin, fats and proteins, to degrade various N-compounds like DNA or arginine, and to reduce nitrates to nitrites were more pronounced in strains from the central upwelling area.