Release Of Dimethylsulfide (DMS) And Dimethylsulfoniopropionate (DMSP) In Marine Algae

Dimethylsulfide (DMS) is the most abundant volatile sulfur compound in the surfaceocean. DMS plays a key role in the global biogeochemical cycle of sulfur and has a greatinfluence on the global climate change and the formation of acid rain. It is mainly producedby the enzymatic breakdown of dimethylsulfonionpropionate (DMSP), which is anabundant compound in phytoplankton.We focus on the production of DMS and DMSP during the growth stages of threetypical offshore algae by laboratory culture experiment. Secondly, we also investigated theinfluence of nutrients on the production of DMS and DMSP in the mesocosm experiment.The results were as follows:1. DMS and DMSP production of three species of marine algaeIn this dissertation, Chaetoceros curvisetus Cleve, Platymonas subcordiformis andPrymnesium parvum Carter were used as experimental materials for the study of DMS andDMSP production during various growth stages in the laboratory experiment. The effects ofvarying levels of salinity, NO3-and SiO32-on algal abundances, DMS and DMSP contentsof these three algae were investigated as these factors were found to be important incontrolling DMSP and DMS dynamics in the seawater. The main conclusions were asfollows:(1) On the whole, the DMSPd and DMSPp concentrations per cell of P.subcordiformis and P. parvum ware higher than those of C. curvisetus.(2) The nitrate had different effects on DMS and DMSP production of the threespecies of algae. High concentration of nitrate stimulated DMS production of P. parvum,while the effects of nitrate concentration on the DMS production of C. curvisetus and P.subcordiformis were not significant. High concentration of nitrate inhibited DMSPproduction of C. curvisetus and P. subcordiformis but had no influence on P. parvum. (3) Higher salinity promoted DMS and DMSP production of P. parvum. DMSP andDMS production were not markedly different in the C. curvisetus, cultures amended withdifferent salinities. Higher salinity stimulated DMSP production of P. subcordiformis, butrestrained DMS production of P. subcordiformis.(4) Lowest SiO32-concentration was helpful to intracellular DMSP accumulation andDMS production of C. curvisetus, compared to medium and highest SiO32-concentrations,2. Influence of nutrients on the production of DMS and DMSP in the mesocosmexperiment.The data of mesocosm enclosure experiment showed that the concentrations ofchlorophylla a in summer was obviously higher than that in autumn, meanwhile the DMSand DMSP release by marine algae was higher than that in autumn. Excessive nitrogen saltincreased the concentration of DMSP. A significant correlation was found between DMSPconcentrations and chlorophylla a levels while the correlation between DMS concentrationsand chlorophylla a levels was not significant.