Of Dms In Seawater Biological Production And Consumption Rate Study

Dimethylsulfide (DMS) is the most abundant volatile sulfur compound in the surface ocean. It has a great influence on the global climate change and the formation of acid rain. The biological production and consumption of DMS are considered to be the principal mechanisms controlling the concentration of DMS in the surface ocean, and play a key role in the global biogeochemical cycle of sulfur. In this dissertation I researched the biological production and consumption rates of DMS in the Yellow Sea. By the laboratory culture experiments, the production of dimethylsulfoniopropionate (DMSP) and DMS during Prymnesiophytes and Skeletonema costatum growing period was studied. Some important conclusions are drawn as follows:ⅰStudy on DMS and DMSP produced by two species of unicellular algaePrymnesiophytes and Skeletonema costatum were selected for the study of DMS and DMSP production during various growing stage by the laboratory culture. The experimental results showed that the production rates of the two algae were different. The average production rate of DMS by Prymnesiophytes was 300 times more than that of Skeletonema costatum. DMSP production had strong correlations with cell numbers. In addition, DMS production had significant correlations with both DMSP and population of cells. DMS and DMSP production rates were different in different algal physiological stages. In the senescent stage, the algae cells produced the largest amount of DMS, which were about eight times more than that of exponential growth phase of Prymnesiophytes and five times more of Skeletonema costatum.The nitrate concentrations have different effects on DMS and DMSP production of the two algae. High nitrate level could stimulate DMS and DMSP production of Prymnesiophytes, but restrain that of Skeletonema costatum. The intracellular DMSP and DMS contents of the two algae increased with increasing salinity of the media. The effects of silicon concentrations on the DMS(P) production of Prymnesiophytes were not significant. ⅱStudy on the biological production and consumption rates of DMS in the Yellow Sea and t factors influencing themThe production rates of DMS in the subsurface water ranged from 2.41 to 10.35 nM?d-1 with an average value of 5.39 nM?d-1. In contrast, the production rates of DMS in the surface microlayer varied from 2.96 to 13.53 nM?d-1 with an average of 7.31 nM?d-1. The consumption rates of DMS in the surface microlayer and subsurface water varied from 2.59 to 9.67nM?d-1, and from 1.89 to 7.13 nM?d-1, respectively. The average values of consumption rates in the microlayer and subsurface water were 5.56 and 4.09 nM?d-1, respectively. The production and consumption rates of DMS were generally higher in the surface microlayer than in the subsurface water. A significant relationship was found between the production rate and the consumption rate of DMS in the microlayer as well as in the subsurface water reflecting a tight biological cycling in these two water bodies.The biological production and consumption of DMS were influenced by various biological and ecological processes and environmental factors such as in situ temperature, salinity, chl-a level and the composition of phytoplankton species.The sea-surface microlayer, as an interface of substance transportation, from the ocean to the atmosphere, plays a key role in the globel biogeochemical cycle of sulfur. This study showed that the escape of DMS to the atmosphere was considered to be one of the principal mechanisms controlling the DMS fates in the microlayer, and the microbial degradation and photochemical oxidation took the second place.ⅲ. Study on the influence of nutrients on the yield and cycle of DMS and DMSP in the mesocosm experiment.The results produced from mesocosm enclosure experiment showed that DMS concentrations in 4 enclosure bags were 3.27 to 4.54 times higher than those in the control bag after nutrients were added put into seawater. NH4+ was more effective than NO3-3-and urea, and excessive nitrogen salt could increase the concentration of DMS too. In contrast, sand dust had little effects on the production of DMS. A significant correlation was found between DMS concentrations and chlorophyll a levels.