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Environmental problems - Chemical approaches
RESEARCH ARTICLE

Influence of vitamin B12 availability on oceanic dimethylsulfide and dimethylsulfoniopropionate

Peter A. Lee A D , Erin M. Bertrand B C , Mak A. Saito B and Giacomo R. DiTullio A
+ Author Affiliations
- Author Affiliations

A Hollings Marine Laboratory, College of Charleston, 331 Fort Johnson Road, Charleston, SC 29412, USA.

B Marine Chemistry and Geochemistry Department, Wood Hole Oceanographic Institution, 360 Woods Hole Road, Woods Hole, MA 02543, USA.

C Biology Department, Dalhousie University, 1355 Oxford Street, Halifax, NS, B3H 4R2, Canada.

D Corresponding author. Email: leep@cofc.edu

Environmental Chemistry 13(2) 293-301 https://doi.org/10.1071/EN15043
Submitted: 7 December 2014  Accepted: 11 September 2015   Published: 23 November 2015

Environmental context. Cobalamin, or vitamin B12, is receiving increased attention as a critical trace nutrient in the growth and metabolic processes of oceanic phytoplankton and bacterial communities. We present evidence that indicates B12 has a more significant role in the biogeochemical cycling of the climatically important compounds dimethylsulfide and dimethylsulfoniopropionate than previously understood. Several possible mechanisms are examined that link cellular-level processes involving B12 to global-scale biogeochemical processes involving the oceanic cycling of dimethylsulfoniopropionate and dimethylsulfide.

Abstract. Evidence is presented showing that dissolved dimethylsulfoniopropionate (DMSPd) and dimethylsulfide (DMS) concentrations are influenced by the availability of vitamin B12 in two oceanographically distinct regions with different DMS production capacities, the central equatorial Pacific Ocean and the Ross Sea, Antarctica. In both locations, addition of B12 to incubation experiments resulted in decreases in DMS and, in some cases, DMSPd concentrations relative to unamended controls. In no case did increasing iron availability significantly (α = 0.1) alter DMS concentrations relative to controls. The relative decreases in DMS between B12 addition and control experiments were significant (α = 0.1) in five of seven experiments conducted at ambient iron levels. Overall, DMS concentrations were on average 33.4 % (±15.1 %; 1 standard deviation) lower, relative to unamended controls, by the end of incubation experiments when B12 was added. Declines in DMSPd were observed in three of five experiments. Similar trends were observed when B12 was added to iron-supplemented bottle incubation experiments (30.4 ± 10.4 % lower final DMS concentrations in +B12Fe treatments relative to +Fe treatments). Several possible molecular-level explanations exist for this link between B12 and DMS production, including potential B12 dependence of methyltransferase enzymes involved in both DMS and DMSP degradation. Although the enzymology of these reactions remains unclear, the relationships described here provide evidence for plausible mechanisms behind the microbial modulation of oceanic DMS.


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