title: Chromophoric dissolved organic matter of black waters in a highly eutrophic Chinese lake: Freshly produced from algal scums?
abstract: Field campaigns and an incubation experiment were conducted to evaluate the sources of chromophoric dissolved organic matter (CDOM) in black water spots in highly polluted regions of the Chinese Lake Taihu. A significant positive correlation (p<0.0001) was found between chlorophyll a (Chl-a) and the CDOM absorption coefficient a(350), indicating that algae degradation was likely the primary source of CDOM in black waters. This is supported by our field results that Chl-a, a(350) and the spectral slope ratio (SR) were significantly higher in the black water samples than in the regular samples (p<0.001). Our incubation experiment further substantiated the primary significance of biological CDOM source where a(350) increased with decreasing Chl-a concentrations. After seven days' incubation, a 72.2% decrease and a 74.9% increase were recorded for Chl-a and a(350), respectively, relative to the initial values. Parallel factor analysis identified five fluorescent components. The maximal fluorescence intensity (Fmax) of tryptophan-like C1 and microbial humic-like C3 of black water samples was significantly higher than in the regular water samples (p<0.0005). This is consistent with incubation experiment results showing a rapid increase in Fmax of the two components, emphasizing the priority of the in situ biological CDOM source in black water spots.
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China; Sino-Danish Center for Education and Research, Beijing 100190, China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Bioscience and Arctic Center, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark; Sino-Danish Center for Education and Research, Beijing 100190, China.
authors.forename: Erik
authors.initials: E
authors.lastname: Jeppesen
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: ylzhang@niglas.ac.cn.
authors.forename: Yunlin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Niu
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Shi
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Guangwei
authors.initials: G
authors.lastname: Zhu
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Boqiang
authors.initials: B
authors.lastname: Qin
mesh_terms: D018533:Biomass; D002681:China; D005068:Eutrophication; D060106:Lakes; D058086:Microalgae / Q000378:metabolism*; D012995:Solubility; D014873:Water Pollutants / Q000378:metabolism*
chemical_list: D014873:Water Pollutants
keywords: Algae block mass/algae degradation; Black water bloom; Chromophoric dissolved organic matter (CDOM); Lake Taihu