Degradation of DMSP in Antarctic winter sea ice: Who is responsible?

Christiane.Uhlig [ at ]


Dimethylsulfoniopropionate (DMSP) is frequently found in high concentrations in polar sea ice, especially when the phytoplankton biomass is high. It is synthesized by various types of phytoplankton and serves, for example, as compatible solute and cryoprotectant, an adaptation to the physico-chemical conditions in sea ice. DMSP can be cleaved to the climate cooling gas dimethylsulfide (DMS) by the phytoplankton or by bacteria. The more common pathway, however, is bacterial demethylation, which leads to the formation of 3-mercaptopropionate and subsequently methanethiol. Different groups of Proteobacteria are known to possess genes for DMSP-cleavage or DMSP-demethylation pathways, or both. Proteobacteria of the gamma-, alpha, and beta-subclass, and members of the Bacteroidetes phylum are the dominating bacterial groups in sea ice. However, DMSP degradation pathways were investigated in oceanic bacterial strains and information on the processes in sea ice is scarce. We performed incubation experiments to investigate DMSP degradation by sea ice bacterial communities during the AWECS (Antarctic Winter Ecosytem Climate Study) cruise on RV Polarstern (ANT29-6) in the Weddell Sea. Sea ice was crushed and submerged in filtered sea water for incubation in gastight 1L glass-bottles at 0°C. The treatments were amended with DMSP and incubated under different light conditions or nutrient additions. During the experiment, DMSP concentrations decreased and DMS concentrations increased. Bacterial growth was higher in the DMSP amended treatments than in control incubations without DMSP addition, and the fraction of gamma-Proteobacteria increased in all treatments. Dominant species were Polaribacter sp. (Flavobacteria), Oleispiera sp. and Colwellia sp. (gamma-Proteobacteria). Model strains of the aforementioned species contain the cleavage pathway gene dddD as well as the demethylation pathway genes in their genome. However, the confirmation of the presence of the DMSP-cleavage and demethylation genes in our incubations is currently still underway.

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Conference (Talk)
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Gordon Research Seminar on Polar Marine Sciences, 14 Mar 2015 - 15 Mar 2015, Barga, Italy.
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Uhlig, C. , Helmke, E. , Damm, E. and AWECS, B. G. (2015): Degradation of DMSP in Antarctic winter sea ice: Who is responsible? , Gordon Research Seminar on Polar Marine Sciences, Barga, Italy, 14 March 2015 - 15 March 2015 .

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ANT > XXIX > 6

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