Vertically resolved cycling of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) in the Northwest Atlantic in spring

In May 1998, profiles of ambient concentration and net changes of particulate dimethylsulfoniopropionate (DMSPp), dissolved dimethylsulfoniopropionate (DMSPd), and dimethylsulfide (DMS) were measured in three bio geographic provinces of the Northwest Atlantic: Northwest Atlantic Continental Shelf (Grand Banks), North Atlantic Drift, and North Atlantic Subtropical Gyre (Sargasso Sea). All stations/depths exhibited large losses of DMSPp (up to 18.0 nmol.L(-1.)day(-1)). DMSP and DMS cycling varied in relation to the type and development stage of the plankton assemblages. The postdiatom bloom conditions on the Grand Banks were associated with an efficient utilization of DMSP by microzooplankton and bacteria. Bacterial DMS production balanced the DMS bacterial consumption, resulting in little net DMS production (0.3 nmol.L(-1.)day(-1)). This contrasted with the North Atlantic Drift and Sargasso Sea stations where flagellates were thriving and most of the DMSPp loss was recovered in the dissolved pool, indicating a less active microbial DMSP metabolism. DMSPd cleavage was high in these latter cases and exceeded DMS bacterial consumption, allowing a net production of DMS (up to 1.8 nmol.L(-1.)day(-1)). These results indicate that maximum DMS net production occurs in growing algal systems where the production of DMSPd resulting from microzooplankton grazing exceeds the bacterial requirement in carbon and sulfur.