Effect of UV- radiation on DMSP content and DMS formation of Phaeocystis antarctica

DMSP (dimethyl sulphonium propionate) contents produced by an Antarctic marine phytoplankton species, Phaeocystis antarctica (Prymnesiophyta), which were incubated under light conditions with radiations of different UV wavebands, were measured by gas chromatography after various exposure times. Full light (UV-B + UV-A + PAR) caused the strongest decrease in the production of DMSP in the alga. A marked depression of DMSP content was also observed with short UV-B and UV-A wavebands after 3 h. It was therefore hypothesised that DMSP production in Phaeocystis antarctica was inhibited by UV radiation. There was a negative correlation on change of DMSP contents under UV radiation. There was a negative correlation on change of DMSP contents under UV radiation with exposure times. The conversion rate of DMSP dissolved to DMS (dimethyl sulphide) was significantly increased with UV radiation. The possibility could not be excluded that a high concentration of free chemical radicals in seawater due to UV radiation resulted in an increase of DMSP cleavage in seawater. The oxidation of DMS in seawater due to UV-B radiation could result in a decrease of its flux to the atmosphere. The effect of UV radiation on DMSP production and oxidation of DMS may be an important factor in the variability of DMSP and the global flux of DMS from ocean to atmosphere.