中文摘要：

对南海北部神狐海域Site 4B站位现代沉积物中脂肪酸组分进行了分离,主要讨论了支链脂肪酸和单不饱和脂肪酸的来源,认为i/a-C15∶0、i/a-C17∶0、16∶1ω5和18∶1ω9来自硫酸盐还原菌（SRB）,而16∶1ω7t/c和18∶1ω7来自硫氧化菌（SOB）。沉积物中SRB和SOB分布形式可能和硫酸盐还原作用生成硫化物、硫化物又被氧化生成硫酸盐和元素硫、元素硫歧化作用生成硫化物和硫酸盐有关,并在整个硫循环系统中SRB起到主导作用;而在95～97cm层位剧增的SRB和SOB生物量与站位附近底辟构造活跃带来深部大量的营养流体有关。

英文摘要：

The lipid biomarkers of fatty acids in Site4 Bsediments from Shenhu Area,Northern South China Sea are studied in this paper and the sources of branched fatty acids and monounsaturated fatty acids are discussed.The results reveal that i/a-C15∶0,i/a-C17∶0,16∶1ω5and 18∶1ω9are derived from sulfate reducing bacteria（SRB）,while 16∶1ω7t/c and 18∶1ω7are originated from sulfur-oxidizing bacteria（SOB）.The distribution of SRB and SOB may be related with the process that sulfate was reduced to sulfide,and then sulfide oxidized to sulfate and element of sulfur,and at last elemental sulfur was disproportionated to sulfide and sulfate.In this process,SRB dominated the sulfur cycle system in the sediments.The increasing biomass of SRB and SOB at depths of 95～97cm is related with diapire structure around Site4 B,which carries a great amount of nutrient fluid.