Characterisation of biogeochemical processes in methane-containing sediments of the Beaufort Sea (Arctic Ocean)

• Main Author: Schweers, Johanna
• Format: Thesis
• Language: English
• Published: 2011
• Subjects: Arctic; Arctic Ocean; Beaufort Sea
• Online Access: https://oceanrep.geomar.de/id/eprint/13574/; https://oceanrep.geomar.de/id/eprint/13574/1/Dipl.%202011%20Schweers,J.pdf

Polar Regions are experiencing and will experience the greatest impact from global change, especially in the Arctic, which has displayed the highest increase in temperature over the last decades. However, the microbial processes in arctic sediments, and how they could be impacted by temperature changes, are still poorly understood. To investigate the microbial processes in arctic sediments and to see if methane releases from sediments are changing with the projected temperature rise, samples were taken from the continental shelf and slope of the Beaufort Sea. Sediment cores from different water depths (ranging from 30 - 2000 m) were collected and the microbial processes of sulfate reduction (SR), anaerobic oxidation of methane (AOM) and methanogenesis (MG) were examined to a maximum sediment depth of ~5 m. First, temperature experiments were conducted to determine in-vitro rates of SR, AOM and MG at a temperature range from -5 to 37 °C. In-vitro rates were measured applying both direct measurements of sulfide and methane development, as well as radiotracer techniques. The ex-situ rates of AOM and SR, which were made on board, displayed additional peaks in the sediment layer where normally only MG would be expected. Second, to examine if, and to what extent, these three processes coexisted in this layer, inhibition experiments with different inhibitors were conducted. The first experiment was carried out with the chemical sodium molybdate, which inhibits SR. The second experiment was performed with 2-bromoethanesulfonate (BES), a substance that inhibits the metabolism of archaea mediating MG and AOM. Lastly, catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) was applied to determine the ratio of bacteria to archaea in the sediment. For this analysis, one sample was examined from three different sediment layers where SR, AOM and MG dominated, respectively. In the sediments of the Beaufort Sea, the SR microbial community showed a psychrophilic to mesophilic metabolism in the surface ...