Bacterial biomasses and activities in the Northwest African upwelling region

During the 'Meteor' expedition SUBTROPEX '82, sediment samples were taken at 14 stations in different water depths at 35, 29, 25, 21 and 17 °N, and measurements of bacterial biomasses and activities were carried out in these different upwelling-intensity areas. Highest densities and biomasses by AODC (2.2 x 10**8 cells, corresponding to 14.8 µg C/g sediment dry wt) were recorded at 21 °N, year-round upwelling, at 1200 and 800 m, but at 500 m biomass was still 4.3 µg C/g dry wt. Relatively high densities and biomasses (6.5 and 6.8 µg C/g dry wt) were found at 17 °N, upwelling mostly in winter and spring, at 1200 and 800 m. AODC were 2 to 3 orders of magnitude higher than viable counts, incubation at 2 or 20 °C. For deep-water sediments, counts at 2 °C were higher than at 20 °C. Biomass and ATP concentrations were highest in the 0 to 2 cm sediment layers; they decreased with sediment depth. Bacterial biomasses were correlated with organic carbon and ATP concentrations. The fractions of Bacterial ATP were calculated to be 2 to 24% of ATP-biomass. On the basis of organic carbon, however, fractions of Bacterial Organic Carbon were only 0.02 to 0.06%. For microbial communities, the conversion factor 0.004 for BOC to BATP seems 2 orders of magnitude too high. Maximum AEC ratios of 0.53 to 0.70 were found at 21 and 17 °N; the other stations had AEC ratios of 0.21 to 0.47. Numbers of bacteria with respiratory ETS were between 0.5 and 10.5 % of AODC. An exception was the shelf station at 35 °N with 34.2% of AODC.