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.

Biogeochemistry (speciation and isotopes of S and C) in bottom sediments, water and bacterial mats from the White Sea

This publication presents results of microbiological and biogeochemical studies in the White Sea. Material was obtained during a series of expeditions in 1999-2002. The studies were carried out in the open part of the White Sea, in the Onega, Dvina and Kandalaksha Bays, as well as in the intertidal zone of the Kandalaksha Bay. Quantitative characteristics of activity of microbial processes in waters and bottom sediments of the White Sea were obtained. The total number of bacteria was equal to 150000-800000 cells/ml, and intensity of dark CO2 assimilation was equal to 0.9-17 µg C/l/day. Bacterial sulfate reduction was equal to 3-150 mg S/m**2/day, and methane formation and oxidation was equal to 13-6840 and 20-14650 µl CH4/m**2/day, respectively. Extremely high values of intensity of all principal microbial processes were found in intertidal sediments rich in organic matter: under decomposing macrophytes, in local pits at the lower intertidal boundary, and in the mouth of a freshwater brook. Average hydrogen sulfide production in highly productive intertidal sediments was 1950-4300 mg S/m**2/day, methane production was 0.5-8.7 ml CH4/m**2/day, and intensity of methane oxidation was up to 17.5 ml CH4/m**2/day. Calculations performed with account for areas occupied by microlandscapes of increased productivity showed that diurnal production of H2S and CH4 per 1 km**2 of the intertidal zone (August) was estimated as 60.8-202 kg S/km**2/day and 192-300 l CH4/km**2/day, respectively.