Potential roles of dimethysulfoxide in regional sulfur cycling and phytoplankton physiological ecology in theNESubarctic Pacific

We measured the concentration and turnover rates of dimethylsulfoxide (DMSO) across the northeast Subarctic Pacific (NESAP) to better understand the role of this compound in regional sulfur cycling and phytoplankton physiological ecology. Using ship-track observations and Lagrangian drifter surveys, we examined the spatial and temporal components of DMS and DMSO variability, comparing rates of DMSO reduction with simultaneous measurements of dimethylsulfide (DMS) oxidation and dimethylsulfoniopropionate (DMSP) cleavage. Our results show high concentrations and rapid turnover of DMSO across much of our NESAP survey region. DMS and DMSO concentrations ranged from < 1 nM to maxima of 26 nM and 183 nM, respectively, and exhibited a nonlinear positive relationship. Rate constants for DMSO reduction to DMS ranged from < 1 to 6.5 d(-1)and were correlated to bacterial production and phytoplankton taxonomic composition. DMSO reduction rates exceeded dissolved DMSP cleavage at nearly all stations, and exceeded DMS oxidation rates at four stations where DMSO reduction and DMS oxidation were measured simultaneously. At these stations, net DMS production from DMSO ranged from 0.50 to 7.18 nM d(-1). During our Lagrangian survey, DMSO concentrations decreased during periods of peak mid-day irradiance. A strong correlation between DMSO concentrations, non-photochemical quenching and photochemical efficiency of photosystem II (F-v/F-m) suggest a potential role for DMSO in photo-protection, supporting previous suggestions of an anti-oxidant function for this molecule. Our findings highlight the potential contribution of DMSO to net DMS production in the NESAP, and suggest a role for this compound in phytoplankton physiological ecology.