Distribution Of Lipid Biomarkers In Sediments From The Red Tide-frequent-occurrence Area In The East China Sea And Their Indications

Nutrient in the East China Sea （ECS） input from the Changjiang River has beenincreasing.Since the1980s,the frequency and intensity of the harmful algae bloom（HAB） in ECS has increased year by year, while the diatom population in the structuredeclined. Phytoplankton primary productivity and population structure changes, andultimately may change the efficiency of the biological pump, thereby affecting thecarbon cycle in the ECS. Thus, taking advantage of the long-term changes in oceanproductivity had great Significance to deepen understanding of the East China Seacarbon cycle and biological pump.Four kinds of biomarker’s composition，including alkanes、Fatty acids、sterols，of the sediment cores at four sites of the red tide-frequent-occurrence area in the EastChina Sea （ESC）, which was examined by GC-MS, and the results of element analyses、stable carbon compositions and Principal Component Analysis （PCA） were combined toinfer organic carbon sources and the shifting of phytoplankton community structures.Experimental data of13C indicate that the terrestrial source of organic carbon inputis basically half and half, the proportion of the source of organic matter input as theburial depth of the shallow rise. C/N ratio can also indicate the contribution of differentsources of organic matter, but can not provide quantitative result, with only theinstructions on the significance of the trend. Also suggests the increased contribution ofmarine phytoplankton in the past two decades sediment organic carbon. N-alkanesdistribute between C₁₄ to C₃₆. The Bimodal distribution pattern and the odd carbonpredominance indicate the marine autogenic and terrestrial inputs.The CPI, TAR, P_mar-aq and other characteristics reflect the input of terrestrialn-alkanes in the survey sea area, primarily herbaceous plants.OEP and CPI values thatza3station by potential oil pollution. Pr/Ph value reflects a sampling of regional sedimentary environment oxidizing environment-based. The fatty acids are the highestconcentrations of lipids in the angae, is also more abundant in the sediments of a class ofbiomarkers. Sampling is controlled by two main factors: terrestrial and marine fattyacids in95%of the sediments. The different types of fatty acids may come from threekinds of material sources：micro-algae, bacteria, terrestrial higher plants, which the algaeand bacteria source for the study area, the main source of fatty acids, the contributionrate in more than75%. Algae contributed more in southern Fujian and Zhejiang coastalmud area. The diatom index inversion diatoms historical trends, to reflect the increasingtrend of red tide in the1980s.At high deposition rate of the inner shelf region, fatty acidsare not well reflect the contribution of terrestrial organic matter. In addition, we can seeby the ratio between the rapeseed sterol dinoflagellate sterol dc11station in the pasthistorical period the proportion of diatoms in the gradually increasing, while the threesouthern stations the proportion of dinoflagellate has increased. Through inversion of thephytoplankton community structure changes in the past30years za3station and foundto be some fluctuations between years, but the overall trend, the proportion ofdinoflagellate increasing. This change and the East China Sea since the red tide since theeighties and nineties of last century by a simple diatom red tide diatom dinoflagellate redtide alternately occurring changes consistent.The above analysis shows that the increased eutrophication of the East China Sea inrecent years on the phytoplankton community structure in sediment in the lipidbiomarker records, lipid biomarkers in sediments can be used as instructed the edge ofthe sea eutrophication status of a means.