MEPS 202:27-40 (2000)  -  doi:10.3354/meps202027

ABSTRACT: The dynamics of the cleavage of dissolved dimethylsulfoniopropionate (DMSP_d) to dimethylsulfide (DMS) were measured experimentally in the surface waters of the Labrador Sea in spring 1997. At in situ DMSP_d concentrations, DMS production and consumption processes were generally in balance. Two stations in the central Labrador Sea displayed net DMS production of approximately 2 nmol l^-1 h^-1, DMSP_d net consumption of 3.48 nmol l^-1 h^-1 and a net DMS production yield from DMSP_d of 60% at near in situ DMSP_d concentrations. Similar to general bacterial substrate utilization in cold waters, DMS production in the Labrador Sea seemed to be temperature and substrate limited. Following DMSP_d additions, linear and non-linear net DMS production were observed. The non-linear response was characterized by a lag in DMS production and was associated with the cold, polar waters of the Labrador and West Greenland Currents. Net DMS production rates measured after DMSP_d addition were proportional to the added amount of DMSP_d. No saturation of the net DMS production rate was observed for concentrations up to 5000 nmol DMSP_d l^-1. First order rate constants determined for these DMS production kinetics suggest an average turnover time of DMSP_d by cleavage to DMS of 3.8 d (2.7 to 5.2 d). At water temperatures of -1.3 to 8°C, potential net DMS production rates measured following DMSP_d additions were comparable and even higher than those previously published for temperate and warm oceanic and coastal regions. The net DMS production potential varied by 1 order of magnitude (1.7 to 18.4 nmol DMS l^-1 h^-1) throughout the study area. Causal links established with path analysis indicate that this potential seemed to be controlled by water temperature and chlorophyll a concentrations.

KEY WORDS: Dimethylsulfide (DMS) · Dimethylsulfoniopropionate (DMSP) · Production rates · Low temperature · Bacteria · Substrate utilization