Sedimentary Of Organic Carbon In The Sediments Of North Yellow Sea: Indicated By Lipid Compounds

The North Yellow Sea is a marginal sea of the northwest Pacific, it carries a hugepressure of human activities and also is a controversial area, few studies had focusedon distribution, migration and degradation of organic carbon in the sediment. Thisthesis concerned on the distribution, origin and transformation of organic carbon inthe sediments indicated by fatty acids and neutral lipids, and discussed influencefactors of behavior of organic carbon in this area.Research showed that the content of organic carbon was0.34~1.43%. The valueof the central region was higher than the coastal area, the coastal area of LiaodongPeninsula was higher than Shandong Peninsula. The distribution of organic carbonwas the same as the chlorophyll a in the water column, which revealed high primaryproductivity of phytoplankton in the central area. The organic carbon ranged at0.74~0.97%in the vertical orientation. The Maximum value appeared at8cm layer,increasing with depth above8cm and reducing to the minimum value in the bottom.Lipids had divided into three forms: free, bound and mineral bound.31fatty acidmolecules existed in this area, including saturated fatty acids(C10:0~C28:0), branchedchain fatty acids(such as i-13:0, i-14:0, et al), monounsaturated fatty acids(such asC16:1, C18:1n9, C18:1n7and C20:1), and polyunsaturated fatty acids (C18:2).25neutral compounds, including phytol, alcohols, and sterols, had been detected.Free fatty acids in surface sediment ranged at6.58~82.24μg/(g dry weight). Freeneutral lipids changed at2.63~43.52μg/(g dry weight). Distribution of fatty acids andneutral lipids were the same as organic carbon. From surface to bottom, fatty acidswas changed between7.57~31.80μg/(g dry weight), and reduced with depthsignificantly. Neutral lipids were4.71~17.14μg/(g dry weight). The highest value wasin the surface layer, while the lowest was in the middle layer. Vertical change of fattyacids were7.57~31.80μg/(g dry weight), and neutral lipids were4.71~17.14μg/(gdry weight), which was reduced with depth. In addition, the bound fatty acids were the main form in the sediment, while free neutral lipids were dominated in the surfacesediment, and bound neutral lipids were dominated in the deep sediment.According to the sources, lipids were from terrestrial high plant, micro algae andbacteria. Organic carbon in the surface sediment was mainly from the primaryproductivities of phytoplankton and phytobenthos. However, in the deep sedimentbacteria were the major producer of lipids. The productions of terrestrial high plantsaccounted for a small proportion.Terrestrial lipids had the process of transportation in the sediment. Differentdistributions of micro algae lipids were concerned with primary productivity.However, they might be transported to the central area. Bacterial fatty acids weremainly controlled by material supply and degradation. In the vertical direction,terrestrial fatty acids were not buried in the deep sediment, and they were differentfrom C24and C26alcohols. The micro algae fatty acids and phytol accumulated inthe deep sediment. The mixing fatty acids were relatively stable in the deep sediment,and the organic matter from multiple sources provided abundant foods for microbes.