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General Session 2: Marine & estuarine biogeochemistry |
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Sources and transformation of dissolved organic matter in the Pearl River Estuary
Tuesday 10th @ 1150-1210
Conference Hall
Wei Chen, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Kai Wu, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Shuai Gu, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Minhan Dai, State Key Laboratory of Marine Environmental Science, Xiamen University
Zhanfei Liu, Marine Science Institute, The university of Texas at Austin, U.S.
Xiaolin Li* , State Key Laboratory of Marine Environmental Science, Xiamen University, China
Presenter Email: xlli@xmu.edu.cn
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| Production and transformation of dissolved organic matter (DOM) control carbon partitioning and transport in productive estuary regions, yet tracing the source and lability of DOM is challenging in this complex environment. Here we identify the sources, transport and lability of DOM from the upper to lower Pearl River Estuary (PRE) in July 2015 by measuring dissolved organic carbon (DOC) and total hydrolyzable dissolved amino acids (TDAA). Bacterial alteration of terrigenous DOM in the upper and mid PRE is inferred from the relatively more abundant glycine and gamma-aminobutyric acid. In the lower PRE, a diatom bloom was observed, which may be triggered by nutrients input from the Pearl River plume. Relatively abundant phenylalanine, glutamic acid, and aspartic acid were found in the surface water of the bloom region, indicating that the production of DOM may be sourced from diatom. Carbon yield of THAA was significantly higher in the lower PRE region than those of upper and mid PRE, indicating the accumulation of labile DOM in the surface water. Based on a mixing model of two end members, DOC was slightly accumulated, while dissolved inorganic carbon (DIC) was significantly removed by primary producer in surface waters of the lower PRE. Also, the accumulated DOC has a positive correlation with DIC deficit (p<0.001) and accounts for ~10% of DIC consumption. However, in the deeper samples of the bloom region, DIC was released and strongly correlates with dissolved oxygen (DO) (slope = 0.9, r2 = 0.89), indicating microbial respiration of labile organic matter. By characterizing DOM composition at molecular level we could identify sources and transformation in dynamic estuarine environments, more research is needed to focus on environmental and inherent factors that control the transformation of DOM. |
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