Lead and cadmium in the Weser Estuary and the German Bight: Correlations between bacteria populations, heavy metals and organic carbon

Organic carbon, lead and cadmium contents of 20 sediments were determined and compared with the colony counts of anaerobic heterotrophic, anaerobic nitrogen fixing, chitinoclastic and cellulolytic bacteria. Organic carbon content, which is dependent on the sediment type, was positively correlated with lead and cadmium as well as with colony counts of all 4 physiological groups of bacteria. Even the sediments with the highest concentrations of 251.7 ppm Pb and 3.1 ppm Cd showed no reduction in their colony counts. From 2 different sediment sampIes with lead contents of 140 ppm and 21 ppm lead tolerance of the aerobic heterotrophic bacteria was investigated. However, no significant difference in lead tolerance of the 2 heterotrophic populations was found. Water from 6 stations was analysed for dissolved and particulate organic carbon, lead and cadmium. Dissolved lead concentrations were in the range of 0.2-0.5 µg/l and the particulate lead contents were between 0.05 and 4.3 µg/l. The concentrations of total lead for the stations off-shore were only one order of magnitude from the concentrations of the near-shore stations. The same phenomenon was observed for dissolved cadmium (0.02 - 0.25 µg/l) and particulate cadmium (0.003 - 0.15 µg/I) concentrations. Correlations between dissolved (1.6 - 10.8 mg/I) and particulate organic carbon (0.25 - 1.53 mg/I) with dissolved and particulate lead or cadmium were not found.

Bacterial production in the eastern Mediteranean Sea in August and September 2008 during SES_GR2

The SES_GR2_MICROBIAL PARAMETERS dataset is based on samples collected in the framework of the project SESAME, in the Ionian, Libyan and Aegean Sea during August-September 2008. The objectives were to measure the standing stocks and calculate the production of the microbial compartment of the food web, describe the vertical distribution pattern and characterize its structure and function through the water column. Bacterial production was estimated by the 3H-leucine method (Kirchman et al. 1986, Kirchman 1993). At each depth, duplicate samples and a control were incubated with 20 nM L-[4,5 3H]-leucine. Samples were incubated in the dark, at in situ temperature.

Seawater carbonate chemistry and phytoplankton and eubacterial community compositions in the northwest subarctic Pacific

On-deck CO2-Fe-manipulated incubation experiments were conducted using surface seawater collected from the Western Subarctic Gyre of the NW Pacific in the summer of 2008 to elucidate the impacts of ocean acidification and Fe enrichment on the abundance and community composition of phytoplankton and eubacteria in the study area. During the incubation, excluding the initial period, the mean partial pressures of CO2 in non-Fe-added bottles were 230, 419, 843, and 1124 µatm, whereas those in Fe-added treatments were 152, 394, 791, and 1008 µatm. Changes in the abundance and community composition of phytoplankton were estimated using HPLC pigment signatures with the program CHEMTAX and flow cytometry. A DGGE fingerprint technique targeting 16S rRNA gene fragments was also used to estimate changes in eubacterial phylotypes during incubation. The Fe addition induced diatom blooms, and subsequently stimulated the growth of heterotrophic bacteria such as Roseobacter, Phaeobacter, and Alteromonas in the post-bloom phase. In both the Fe-limited and Fe-replete treatments, concentrations of 19'-hexanoyloxyfucoxanthin, a haptophyte marker, and the cell abundance of coccolithophores decreased at higher CO2 levels (750 and 1000 ppm), whereas diatoms exhibited little response to the changes in CO2 availability. The abundances of Synechococcus and small eukaryotic phytoplankton (<10 µm) increased at the higher CO2 levels. DGGE band positions revealed that Methylobacterium of Alphaproteobacteria occurred solely at lower CO2 levels (180 and 380 ppm) during the post-bloom phase. These results suggest that increases in CO2 level could affect not only the community composition of phytoplankton but also that of eubacteria. As these microorganisms play critical roles in the biological carbon pump and microbial loop, our results indicate that the progression of ocean acidification can alter the biogeochemical processes in the study area.