Bacterial biomasses and activities in the Northwest African upwelling region

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.