Abstract. A database of 15,617 point measurements of dimethylsulfide (DMS) in surface waters along with lesser amounts of data for aqueous and particulate dirhethylsulfoniopropionate concentration, chlorophyll concentration, sea surface salinity and temperature, and wind speed has been assembled. The database was processed to create a series of climatological annual and monthly 1øxl ø latitude-longitude squares of data. The results were compared to published fields of geophysical and biological parameters. No significant correlation was found between DMS and these parameters, and no simple algorithm could be found to create monthly fields of sea surface DMS concentration based on these parameters. Instead, an annual map of sea surface DMS was produced using an algorithm similar to that employed by Conkright et al. [1994]. In this approach, a first-guess field of DMS sea surface concentration measurements is created and then a correction to this field is generated based on actual measurements. Monthly sea surface grids of DMS were obtained using a similar scheme, but the sparsity of DMS measurements made the method difficult to implement. A scheme was used which projected actual data into months of the year where no data were otherwise present.

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Abstract. During 1991-1995, seven voyages were made to the Southern Ocean to determine the distribution of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in seawater and air in the Australasian sector (60øE to 165øE). Measurements of DMSP in sea ice were also made. During the summer months the Subtropical Convergence (STC) and Antarctic Convergence (AC) were identified as important source regions of these sulfur compounds. In the Seasonal Ice zone (SIZ) there were marked longitudinal differences possibly reflecting higher productivity and the extent of the sea ice in this region. Levels of DMSP in sea ice cores were consistent with this regional difference. High and variable concentrations of DMSP also occurred in the Subantarctic Zone (SAZ) (45ø-53øS), decreasing to lower levels around 64øS, close to the Antarctic Divergence (AD). Upwelling of deep water around the AD is suggested to have been responsible for the low biological activity and low DMSP levels. While there was generally a good relationship between DMSPp and biomass, there was a marked difference in the DMSPp:chlorophyll a ratio between regions, and between years. DMSP was generally negatively correlated with dissolved nitrate, however, it was unclear if the level of nitrate directly affected DMSP production. DMSw levels were highest in the mixed layer, with lower, yet detectable, levels in the deeper ocean. DMSw was occasionally elevated in Antarctic Bottom Water (AABW), suggesting that ice shelf water transports this substance to deeper waters. DMSP was not found above detection limits below the mixed layer, but some evidence was found that DMSP may be transported to deeper waters, close to the Antarctic continent.

Biogenic dimethylsulfide (DMS) and its main precursors, dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO), are potential scavengers of reactive oxygen species in marine algae, and these dimethylated sulfur compounds (DSC) could take part in the algal antioxidant system. In this study, a link between the DSC production and the antioxidant capacity (AOC) of Acropora aspera reef coral was investigated under a range of environmental factors (temperature, light, salinity, and air exposure) that can lead to oxidative stress in the coral holobiont. Enhanced DMS(P)(O) production occurred under experimental conditions, indicating that DSC are potential biomarkers of stress level in coral tissue. Differences in concentrations and partitioning as a response to different treatments suggest that DSC production and turnover undergo different biochemical pathways depending on the type and severity of environmental stress. Osmotic pressure and light depletion led to an upregulation of the coral AOC that was correlated with a significant increase in DMSO : DSC ratio. These results, combined with a positive correlation between the AOC and DMSO concentrations under these two treatments, suggest that the DMSP-based antioxidant system is involved in the overall antioxidant regulation of the coral holobiont. Enhanced DMS production coupled with an increased DMS : DSC ratio under increased temperature indicated that thermal stress triggers DMS formation in coral tissue. Considering the role that DMS can have in both climate regulation and the DMSP-based antioxidant system, our findings highlight the need to further examine the fate of DSC in coral reef environments under scenarios of increasing sea surface temperatures.