AME 18:197-205 (1999)  -  doi:10.3354/ame018197

ABSTRACT: We examined microbial production and consumption of dimethyl sulfide (DMS) in Labrador Sea surface waters ranging in temperature from -0.1 to 6.9°C. 200 nM dimethyl disulfide (DMDS) was used to inhibit DMS consumption. We also studied DMS consumption kinetics by additions of 5 to 50 nM DMS, DMS production from added dimethylsulfoniopropionate (DMSP), and DMS production and consumption during zooplankton grazing. During the cruise, DMS concentrations were low, ranging from 1 to 7 nM throughout the study area, which included a bloom of the colonial haptophyte alga Phaeocystis pouchetii. DMDS additions often revealed rapid DMS production and consumption (up to 5 nM d^-1) and very rapid turnover (<1 to 3 d), similar to rates found in coastal waters at much higher temperatures. There was no clear effect of temperature on DMS consumption; rather, DMS consumption appeared to be tightly coupled with production. Turnover was most rapid at low DMS concentrations, and DMS consumption was stimulated by additions of DMS, or by increased DMS production from additions of dissolved DMSP. DMDS additions to zooplankton grazing incubations revealed rapid gross DMS production and consumption which were nearly balanced, resulting in net steady-state DMS patterns. DMDS did not affect production or grazing of algal pigments or DMSP. DMS consumption saturated at 18 to 32 nM [DMS] and saturation kinetics were similar within the photic zone, but consumption was near-zero at greater depths. We suggest that DMS consumption likely saturates more easily than microbial DMS production from DMSP, and this, combined with temperature limitation on the growth of prokaryotic DMS consumers, may lead to the periodic buildup of high DMS concentrations previously observed in polar and subpolar waters.

KEY WORDS: Dimethyl sulfide · Dimethylsulfoniopropionate · DMSP · DMS · Inhibitor technique · Consumption kinetics · Zooplankton grazing