Study on Dimethylsulfide production by phytoplankton based on time-serial observations in the Antarctic Ocean

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Dimethylsulfide (DMS) is the most abundant form of volatile sulfur in the ocean. According to the CLAW hypothesis (Charlson et al. 1987), marine DMS production may act as a climate regulatory mechanism via a feedback loop involving surface ocean temperature, phytoplankton, DMS, sulfate aerosol formation, and cloud albedo, although the existence of this feedback has not been proven. Recently, attention has been focused on assessing sinks and sources of DMS in the oceans and on the processes controlling the cycling of DMS in the marine environment. DMS is produced by the enzymatic cleavage of dimethylsulfoniopropionate (DMSP), an organic compound synthesized by many phytoplankton species. The objective of this study was to determine the influence of biological processes on DMS dynamics in the Antarctic Ocean during the summertime, based on the time-serial observations in the austral summers of 2002/03, 2003/04, and 2004/05. The field data collected in the present study was synthesized in 2005. The present results show that sloppy feeding by Antarctic krill, which is the dominant herbivorousis macrozooplankton of the Antarctic Ocean, a more likely mechanism for producing DMS and dissolved DMSP. Moreover growth phase seems to be related DMSP production by diatoms. This may result in the low concentrations of dissolved DMSP observed in the early stage of diatom blooms under natural conditions. Since these processes on biological production as well as DMS and DMSP production are seem to be affected by variations of sea ice distribution, further study must be required to fully understand the global environment change.