Marine Geochemistry of Dimethylsufide

本研究将探讨海水中二甲硫化物（DMS）的生物地球化学循环。海洋是向全球大气排放生物硫的主要来源，其水平大致相当于人为二氧化硫排放。DMS约占海洋生物硫通量的90%。本研究的目的是阐明海洋中DMS形成、转化和消耗的速率、途径和过程。这种生物地球化学信息对于理解在野外观察到的DMS浓度曲线至关重要，并可能影响未来的采样策略。一个规模更大，更全面地了解DMS的海洋生物地球化学和DMS在海水中循环的过程，将有助于确定海洋生物地球化学过程与挥发性生物源硫化合物的产生之间的关系，而挥发性生物源硫化合物在全球大气硫循环中起着重要作用。本文将讨论以下四种假说：1)海藻二甲基磺酰丙酸盐（DMSP， DMS前体）的降解和DMS的释放是浮游植物正常代谢过程的结果；2) DMS释放结果对浮游植物形成生理胁迫；3)微生物降解含DMSF的藻类物质是海水中DMS的来源之一；4)微生物降解是海水中DMS的汇。评估这些假设的方法将结合实验室和现场孵化实验。实验室研究将在受控的环境条件下进行，并选用个别和混合培养的藻类和细菌物种。实验条件将改变，以检查可能对DMS循环很重要的特定因素。然后将使用实地研究来检查自然条件下的过程。

The proposed research will investigate the biogeochemical cycle of dimethylsulfide (DMS) in seawater. The ocean is a major source of biogenic reduced sulfur to the global atmosphere, at a level roughly equivalent to anthropogenic SO2 emissions. DMS accounts for some 90% of the marine biogenic sulfur flux. The objective of this investigation is to elucidate the rates, pathways, and processes involved in the formation, transformation, and consumption of DMS in the ocean. This biogeochemical information is vital to understanding the DMS concentration profiles which have been observed in the field and may influence future sampling strategies. One a larger scale, a fuller understanding of the marine biogeochemistry of DMS and the processes involved in DMS cycling in seawater will aid in defining the relationship between oceanic biogeochemical processes and the production of the volatile biogenic sulfur compound which plays a major role in the global atmospheric sulfur cycle. Four working hypotheses will be addressed: 1) Degradation of algal dimethylsulfoniopropionate (DMSP, the DMS precursor) and release of DMS is the result of normal metabolic processes by phytoplankton; 2) release of DMS results form physiological stress on the phytoplankton; 3) microbial degradation of DMSF- containing algal material is a source of DMS in seawater; 4) microbial degradation is a sink of DMS in seawater. The approach to assessing these hypotheses will combine laboratory and field incubation experiments. Laboratory studies will be conducted under controlled environmental conditions and using selected individual and mixed culture algal and bacterial species. Experimental conditions will be varied to examine specific factors which may be important in DMS cycling. Field studies will then be used to examine the processes under natural conditions.