Microbiological and Biogeochemical Studies of Microbial Mn(IV) and Fe(III) Reduction in Arctic Sediments (Svalbard)

• Main Author: Vandieken, Verona
• Other Authors: Lemke, Peter, Joergensen, Bo Barker, Schlitzer, Reiner
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2005
• Subjects: microbial Mn and Fe reduction; Svalbard; psychrophilic Fe-reducing bacteria; Arctic marine sediments; organic carbon oxidation; 579; ddc:579; Arctic; Smeerenburgfjorden; Arktis*; Smeerenburgfjord*
• Online Access: https://media.suub.uni-bremen.de/handle/elib/2157; https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000100320

This PhD thesis focuses on the importance of microbial Mn(IV) and Fe(III) reduction for the degradation of organic material in Arctic sediments. Important regulatory mechanisms of microbial Mn and Fe reduction in Arctic sediments were identified by comparing different sediments of a fjord and the northeast coast of Svalbard. By the isolation and characterization of Mn- and Fe-reducing bacteria their potential in situ activities and their adaptation to environmental settings were investigated. The four investigated sites, a fjord of the west coast of Svalbard (Smeerenburgfjorden) and three sites at the northeast coast, were characterized by low bottom water temperatures between 2 and 3°C. Total oxygen uptake and anaerobic carbon oxidation rates of Smeerenburgfjorden sediment were as high as in comparable permanently cold and temperate sediments indicating that the microbial community is adapted to the permanently low temperature. In comparison the oxygen uptake and anaerobic carbon oxidation rates of the three sediments at the northeast coast of Svalbard were lower. At the northeast coast of Svalbard the carbon supply to the sediments is very limited due to long periods of, restricting primary production. In contrast the west coast is influenced by relatively warm Atlantic water and a higher deposition of organic material to the sea floor. Thus, the benthic microbial community of the northeast coast of Svalbard is probably limited by the organic carbon contents of the sediments. Microbial Fe reduction accounted for 43% of the anaerobic carbon oxidation at 0-5 cm depth of Smeerenburgfjorden sediment. The zone of microbial Fe reduction overlapped in the surface sediment of the uppermost 2 cm with the zone of sulfate reduction. High rates of organic carbon mineralization lead to a rapid depletion of Fe(III). Thus, the bacterial Fe-reducing community seemed to be mainly limited by Fe(III). Below 2 cm depth sulfate was sole electron acceptor. Due to low concentrations of solid Mn, Mn was suggested to be mainly reduced ...