Dynamics of dimethylsulfide production from dissolved dimethylsulfoniopropionate in the Labrador Sea

The dynamics of the cleavage of dissolved dimethylsulfoniopropionate (DMSPd ) to dimethylsulfide (DMS) were measured experimentally in the surface wate rs of the Labrador Sea in spring 1997. At in situ DMSPd concentrations, DMS production and consumption processes were generally in balance. Two statio ns in the central Labrador Sea displayed net DMS production of approximatel y 2 nmol 1(-1) h(-1), DMSPd net consumption of 3.48 nmol 1(-1) h(-1) and a net DMS production yield from DMSPd of 60% at near in situ DMSPd concentrat ions. Similar to general bacterial substrate utilization in cold waters, DM S production in the Labrador Sea seemed to be temperature and substrate lim ited. Following DMSPd additions, linear and non-linear net DMS production w ere observed. The non-linear response was characterized by a lag in DMS pro duction and was-associated with the cold, polar waters of the Labrador and West Greenland Currents. Net DMS production rates measured after DMSPd addi tion were proportional to the added amount of DMSPd. No saturation of the n et DMS production rate was observed for concentrations up to 5000 nmol DMSP d 1(-1). First order rate constants determined for these DMS production kin etics suggest an average turnover time of DMSPd by cleavage to DMS of 3.8 d (2.7 to 5.2 d). At water temperatures of -1.3 to 8 degrees C, potential ne t DMS production rates measured following DMSPd additions were comparable a nd even higher than those previously published for temperate and warm ocean ic and coastal regions. The net DMS production potential varied by 1 order of magnitude (1.7 to 18.4 nmol DMS 1(-1) h(1)) throughout the study area. C ausal links established with path analysis indicate that this potential see med to be controlled by water temperature and chlorophyll a concentrations.