4.3 Article

Historical reconstruction of organic carbon inputs to the East China Sea inner shelf: Implications for anthropogenic activities and regional climate variability

Journal

HOLOCENE
Volume 25, Issue 12, Pages 1869-1881

Publisher

SAGE PUBLICATIONS LTD
DOI: 10.1177/0959683615591358

Keywords

anthropogenic activity; chloropigment; East China Sea; lignin; organic carbon; regional climate variability

Funding

  1. National Natural Science Foundation of China [41176063, 41221004]
  2. 111 project [B13030]

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A gravity core collected from the East China Sea (ECS) inner shelf was analyzed for elemental and stable isotopic composition, lignin-phenols, and sedimentary pigments to investigate changes of organic carbon (OC) inputs during the past two centuries. In particular, we examined the linkages between terrestrial and marine OC inputs with climate variability and anthropogenic activities. The decrease of terrestrial OC contribution (from 41% to 28%) and increasing diagenetic indices of lignin-phenols (P/(S+V): from 0.12 to 0.22; 3,5-Bd/V: from 0.03 to 0.09) after the 1970s were possibly attributed to intensified deforestation, dam construction, and channel erosion. Lignin content ((8)) ranged from 0.35mg/100mg OC to 6.92mg/100mg OC, with lower values corresponding to the worst flooding events in the Changjiang watershed and weaker East Asian Winter Monsoon (EAWM), while higher (8) was more correlated to the strengthening of EAWM. This indicates that terrestrial inputs to Zhe-Min Coast are different from those in Changjiang Estuary during flooding events and strongly linked with regional climate variability. The total contents of sedimentary chloropigments (i.e. pheophorbide-a, pheophytin-a, pyropheophytin-a, sterol chlorin esters, and carotenol chlorin esters) ranged from 663.4 to 74.9nmol g(-1) OC, and decreased exponentially downwards. Sedimentary chloropigments that were used to document historical change of phytoplankton biomass were decoupled with historical changes of Changjiang riverine nutrient inputs but corresponded well to the fluctuation of regional climate variability. Higher phytoplankton biomasses usually were observed during positive phases of Pacific Decadal Oscillation (PDO) and/or warm El Nino-Southern Oscillation (ENSO) events, and lower algal biomass usually corresponded to the negative phase of PDO and/or cold ENSO events.

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