Concentrations of total dimethylsulfoniopropionate (DMSPt) and its degradation products, dissolved dimethylsulfide (DMS) and dimethylsulfoxide (DMSOd), were measured in surface waters along three transects between 49 to 768S latitude (November 2003& 2005 and December 2004 in the New Zealand sector of the Southern Ocean. Most water samples were collected from the ships underway pump system, and concentrations of DMSPt, DMS and DMSOd obtained with this method showed excellent agreement with Niskin bottle-collected samples. Dissolved DMSP (DMSPd), on the other hand, was significantly higher in pump samples. Biological consumption rates for DMSPd and DMS were also measured in Niskin-collected surface waters at selected stations. Concentrations of DMSPt (12 to 52 nM) and DMS (0.6 to 3.2 nM) were moderate in open waters north of the seasonal sea ice (north of 638S), and very low (< 12 nM DMSPt and < 1 nM DMS) where sea ice coverage was >80 % (65 -738S; November transects). High concentrations of DMSPt (up to 95 nM) and DMS (up to 30 nM), and high DMS:DMSPt ratios, were observed on the northern boundaries of the seasonal sea ice (63 to 688S) and in the northern Ross Sea (74 -768S). Surface water DMSOd concentrations were variable (1 -55 nM), but generally higher in ice melt zones and the northern Ross Sea, especially in summer (December 2004). Rates of biological DMS and DMSPd consumption were elevated in ice melt zones, but were generally quite low (< 1 nM DMS d -1 and < 2.5 nM DMSPd d -1 ), except in the Ross Sea polynya where consumption rates reached 7 nM DMS d -1 and 13 nM DMSPd d -1 . This data set provides much needed information regarding the distribution and cycling of DMSP, DMS and DMSO in a poorly studied area of the Southern Ocean. Our findings show that areas of ice melt and the northern Ross Sea are zones of elevated DMS concentrations and sea-air fluxes and also rapid cycling of DMSP and DMS.

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The abundant marine organosulfur compound, dimethylsulfoniopropionate (DMSP) can be degraded to acrylate and dimethylsulfide (DMS), with some DMS further oxidized to dimethylsulfoxide (DMSO). Despite intensive study of DMSP and DMS in a variety of marine settings, the processes affecting acrylate and DMSO concentrations in marine waters are poorly known, particularly their loss from the dissolved phase through biological uptake. We measured the concentrations of dissolved acrylate (acrylate d ) and DMSO (DMSO d ) in coastal and open-ocean waters of the northern Gulf of Mexico during non-bloom conditions and quantified the rates and kinetics of their biological uptake using 14 C labeled substrates. Acrylate d concentrations and uptake rates ranged from 0.8-2.1 nmol L 21 and 0.07-1.8 nmol L 21 d 21 , respectively. Somewhat higher uptake rates were observed for DMSO d (0.27-3.9 nmol L 21 d 21 ) owing to higher DMSO d concentrations (5.5-14 nmol L 21 ). Both compounds were taken up by the microbial community with high affinity uptake systems, with similar K s and V max values to those for other well-studied biological substrates including amino acids and monosaccharides. However, median turnover times were relatively slow, 4.8 d for acrylate d and 7.4 d for DMSO d . The slow acrylate d turnover points to low supply rates of this compound to the dissolved phase, a finding consistent with previous observations that the microbial DMSP lyase pathway accounts for only a small fraction of dissolved DMSP degradation (and therefore acrylate production) in the Gulf of Mexico.