Microbial controls on DMSP degradation and DMS formation in the Sargasso Sea |
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Authors: | Maria Vila-Costa Johanna M. Rinta-Kanto Rachel S. Poretsky Shulei Sun Ronald P. Kiene Mary Ann Moran |
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Affiliation: | 1. Department of Marine Sciences, University of Georgia, Athens, GA, 30602-3636, USA 2. Limnological Observatory of the Pyrenees (LOOP) – Department of Ecology, University of Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain 3. Department of Environmental Chemistry, IDAEA-CSIC, Barcelona, Catalonia, Spain 5. Division of Microbiology, Department of Food and Environmental Sciences, University of Helsinki, 00014, Helsinki, Finland 6. Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, 60607, USA 7. Center for Research in Biological Systems, University of California San Diego, 9500 Gilman Drive #0446, La Jolla, CA, 92093-0446, USA 4. Department of Marine Sciences, University of South Alabama, Mobile, AL, 36688, USA
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Abstract: | Bacterial degradation of dimethylsulfoniopropionate (DMSP) represents one of the main sources of the climatically–active trace gas dimethylsulfide (DMS) in the upper ocean. Short-term enrichment studies to stimulate specific pathways of DMSP degradation in oligotrophic waters from the Sargasso Sea were used to explore regulatory connections between the different bacterial DMSP degradation steps and determine potential biological controls on DMS formation in the open ocean. Experiments were conducted with surface water at the BATS station in the western North Atlantic Ocean. We added selected organic substrates (25 nmol L?1 final concentration) to induce different steps of DMSP degradation in the microbial community, and then measured DMSP dynamics (assimilation and turnover rates), DMS yields (using 35sulfur-DMSP tracer), and bacterial production rates. In most treatments, the main fate of consumed S-DMSP was excretion as a non-volatile S product. 35S-DMSP tracer turnover rates (accumulation + assimilation + excretion of transformed products as DMS or others) increased upon addition of DMSP and glucose, but not acrylate, methymercaptopropionate (MMPA), methanethiol, DMS or glycine betaine. DMS yields from 35S-DMSP never exceeded 16 % except in a short term DMSP enrichment, for which the yield reached 45 % (±17 %). Results show that availability of non-sulfur containing labile C sources (glucose, acrylate) decreased bacterial DMS production while stimulating bacterial heterotrophic production, and suggest an influence of bacterial sulfur demand in controlling DMS-yielding pathways. However, regulatory effects on 35S-DMSP fate were not consistent across all reduced sulfur compounds (i.e., methanethiol or MMPA), and may reflect alternate roles of DMSP as a bacterial energy source and osmolyte. |
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