Effects of Light Intensity and Salinity Levels on Dimethylsulfoniopropionate Production in the Potentially Toxic Dinoflagellate Species, Gambierdiscus belizeanus and Gambierdiscus carolinianus

Dinoflagellates are recognized as one of the major marine phytoplankton groups that produce non-volatile dimethylsulfoniopropionate (DMSP). DMSP is the precursor of volatile dimethylsulfide (DMS), a compound affecting atmospheric chemistry and the global climate. Minimal data exist on DMSP production in the dinoflagellate genus Gambierdiscus, and the physiological function of DMSP in this group of potentially toxic organisms is unknown. I therefore examined production of DMSP in two species of Gambierdiscus: G. belizeanus and G. carolinianus, under two irradiances and salinities as a first step towards understanding the function and role of DMSP. My evidence suggests that exponentially-growing G. belizeanus and G. carolinianus did not significantly increase per cell DMSP production or intracellular DMSP concentrations in response to higher light intensity, but that DMSP:Chl a.did increase. Per cell DMSP and intracellular DMSP concentrations in G. belizeanus were significantly higher in cultures grown at 36 ppt salinity compared to 30 ppt, whereas DMSP production by G. carolinianus was not affected by salinity. These two species produced very high intracellular concentrations of DMSP (51-302 mM) indicating DMSP is a major osmolyte in these species. Per cell DMSP values are at or above the highest yet reported in dinoflagellates.