期刊
CONTINENTAL SHELF RESEARCH
卷 203, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.csr.2020.104158
关键词
Sediment; Organic matter; Stable isotope; Spatio-temporal distribution; Seasonal variations; Yangtze river estuary (YRE)
类别
资金
- National Natural Science Foundation of China [31872568]
- Natural Science Foundation of China-Shandong Joint Fund for Marine Ecology and Environmental Science [U1606404]
Riverine supply of largely terrestrial carbon is important to the carbon cycle chemistry of the oceans. Along a river-ocean continuum, sedimentary organic matter composition and distribution can provide insights to the balance of terrestrial input and in situ production of an estuary. In the Yangtze River estuary (YRE), this balance is especially important to understand as human impacts and climate change continue to modify processes along the continuum. Here we discuss the sources and spatio-temporal distributions of organic matter in the coastal ocean surface sediments and how environmental factors have affected changes there. The isotopic compositions (delta C-13 and delta N-15), total organic carbon (TOC), and total nitrogen (TN) of surface sediments were investigated along with sediment grain size and bottom water temperature, salinity, and total suspended matter. Evidence suggests that fine sedimentary grain size, bottom water temperature, and the circulation dynamics of water masses such as Changjiang Diluted Water (CDW) and Taiwan Warm Current (TWC) were the main factors affecting spatial and temporal distributions, with organic matter concentrations in autumn showing higher than that in spring and nearshore areas higher than offshore. An isotopic-based two end-member mixing model suggests that terrigenous inputs were the main source (about 53%) of organic matter in the YRE, followed by autochthonous marine organic matter, in both seasons. Terrestrial organic matter distribution, controlled by the CDW, decreased seaward from the mouth, as expected, and the proportion of terrestrial organic carbon increased in autumn compared to spring. Intrusions of the TWC water likely contributed to the increase of marine components in a tongue-shaped area during both seasons.
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