| The East China Sea is typical river-dominated ocean margins (RiOMar), thebiogeochemistry process is complicated due to the organic matter is settlement,buried and converted in this system. Lipid matters are useful biomarkers in RiOMar.They can be not only used to reconstruct shifting of communication and primaryproduction, and also to indicate the organic matters source and fate.In this study, one sediment core and19surface sediments were collected fromthe red tide-frequent-occurrence area in the East China Sea and Zhou Shan Islands,respectively. TOC、TN、C/N、δ13C and lipids biomarkers were measured, andcombined the Principal Component Analysis to show organic matters sources andthe changing of phytoplankton communication. The main results were shown below:(1) The data of δ13C the core and surface samples indicate that the input both ofterrestrial and marine, especially the marine input. Due to the organic mattersdegradation and microbial activities, the C/N no well reflect the organic matterssource, but can be instructions on the trend change. For core sample, organic mattersproportion increased derived from marine input in the modern sediments. Thesample from about1905~2011yaer, age over100years. For surface sediments, TOCand TN content were similar, and the content spatial distribution shown near-shorehigh and offshore low.(2) For lipid biomarkers of core samples, the n-alkanes shows bimodaldistribution and the predominant of high molecular weight and the odd carbonpredominance reflect the terrestrial-marine mixing inputs. The CPI、TAR、Pmar-aqreflect terrestrial input are prominent, primarily herbaceous plants. Pr/Ph reflect thesampling of regional sedimentary reductive environment, but56~64cm shows strong oxidizing environment. Carbon number of fatty acids between C11~C31, the typicalbimodal distribution shows terrestrial-marine mixed input, especially the marineautogenic. The PCA shows that89%information of the fatty acids controlled by twomain factors, marine input (algae and bacteria) is the main source. Compared theanalysis of fatty acids and n-alkanes, part high molecular weight of n-alkanesderived from aerosols. The linear alkyl alcohol controlled by terrigenous higherplant, marine algae and bacteria, but the mainly is marine algae. The ratio betweendinoflagellates sterol and rapeseed sterol shows the proportion of dinoflagellatesincreasing gradually for a period of time in the past historical. Through inversion ofthe phytoplankton communication structure changes in the past over100yearsZC13station, the result shows that overall trend the proportion of dinoflagellatesincreasing. This results consistent with the single diatom-red tides turn into complexred tides composed of diatoms and dinoflagellates since the80s and90s of the lastcentury.（3）For the lipids of surface sediments, the n-alkanes shows bimodaldistribution and high molecular weight and the odd carbon are predominance. Thecontent distribution trend of∑C15-21and∑C25-35is similar, present the characteristicsof near-shore high and offshore low, this result may be associated with sedimentparticle size, particle size is liable to adsorption organic matter which the marine andterrestrial have high value. The CPI、TAR、Pmar-aq reflect terrestrial input areprominent, primarily herbaceous plants. OEP values indicate no found the oilpollution. Fatty acids distribution shows that the predominant of low molecularweight reflect marine autogenic is advantaged. The PCA shows that91.7%information of the fatty acids controlled by three main factors, marine input (algaeand bacteria) is the main source. Due to the effect of bacteria degradation, thecorrelation of TOC and the fatty acids is poor, so fatty acids not well reflect theterrigenous organic matter input. The ratio of rapeseed sterol-dinoflagellates steroldisplay the dinoflagellates as the dominant species in research area, the farther offshore and the proportion higher of rapeseed sterol, this may be related to broughtrich nutrient through upwelling and Taiwan warm current. |
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