Physiological and ecological role of Dimethylsulfoniopropionate (DMSP) on psychrophilic phytoplankton

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Dimethylsulfoniopropionate (DMSP) production by psychrophilic phytoplankton was experimentally analyzed in order to investigate its physiological and ecological role on phytoplankton. DMSP : chl.a ratios were calculated as indices of DMSP productivities against algal biomass. DMSP productivities were species-specific, i.e. some psychrophilic diatom strains cultured under cold conditions produced DMSP in their cells, and some of them did not produce DMSP. Some of DMSP producing diatoms increased their DMSP productivities during their stationary growth phase. This growth-related DMSP productivity by diatoms may result in the high concentrations of DMSP observed in the later stage of diatom blooms under natural polar seas, and may affect their survival and the succession of species. The environmental effects, such as water temperature and salinity, on phytoplankton DMSP productivities were also investigated. During a laboratory study, water temperature did not affect DMSP productivities in the range of 1.7-5℃. DMSP productivities of diatom strains were tend to be higher under high salinity culture conditions. Especially, Haslea sp. and Navicula sp. produced much DMSP when they grew under 35.2 high saline waters. They are known as icealgae. It is possible that although they produce much DMSP while they grow in the brine waters (high salinity), once they come out from the ice to the melt water (low salinity), they would not produce DMSP. DMSP functions as an osmolyte in phytoplankton, however, it is suggested that phytoplankton would use DMSP as an osmolyte when they grow higher salinity waters and they would use different chemicals to prevent from an osmotic shock when they grow lower salinity waters.