title: Comparison of bacterial growth in response to photodegraded terrestrial chromophoric dissolved organic matter in two lakes.
abstract: Terrestrial chromophoric dissolved organic matter (CDOM) could subsidize lake food webs. Trophic state and altitude have a pronounced influence on the CDOM concentration and composition of a lake. The impact of future changes in solar radiation on high-altitude lakes is particularly alarming because these aquatic ecosystems experience the most pronounced radiation variation worldwide. Photodegradation experiments were conducted on terrestrial CDOM samples from oligotrophic alpine Lake Tiancai and low-altitude eutrophic Lake Xiaohu to investigate the response of bacterial growth to photodegraded CDOM. During the photo-irradiation process, the fluorescent CDOM intensity evidently decreased in an inflowing stream of Lake Tiancai, with the predominance of humic-like fluorescence. By contrast, minimal changes were observed in the riverine CDOM of Lake Xiaohu, with the predominance of protein-like fluorescence. The kinetic constants of photodegradation indicated that the degradation rate of terrestrial (soil) humic acid in Lake Tiancai was significantly higher than that in Lake Xiaohu (p<0.001). Soil humic and fulvic acids irradiated in the simulated experiment were applied to incubated bacteria. The specific growth rate of bacteria incubated with soil humic substances was significantly higher in Lake Tiancai than in Lake Xiaohu (p<0.05). Furthermore, the utilizing rate of dissolved oxygen (DO) confirmed that the DO consumption by bacteria incubated with terrestrial CDOM in Lake Tiancai was significantly greater than that in Lake Xiaohu (p<0.05). In summary, the exposure of terrestrial CDOM to light significantly enhances its availability to heterotrophic bacteria in Lake Tiancai, an oligotrophic alpine lake, which is of importance in understanding bacterial growth in response to photodegraded terrestrial CDOM for different types of lakes.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China. Electronic address: ylsu@niglas.ac.cn.
authors.forename: Yaling
authors.initials: Y
authors.lastname: Su
authors.affiliation: Shaanxi Provincial Academy of Environmental Science, 49 North Changan Road, Xian 710061, China.
authors.forename: En
authors.initials: E
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China.
authors.forename: Muhua
authors.initials: M
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China.
authors.forename: Yongdong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China.
authors.forename: Feizhou
authors.initials: F
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China.
authors.forename: Zhengwen
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000531:Altitude; D001419:Bacteria / Q000254:growth & development*; D004784:Environmental Monitoring; D005453:Fluorescence; D006812:Humic Substances; D060106:Lakes / Q000382:microbiology*; D010782:Photolysis; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D006812:Humic Substances; D014873:Water Pollutants
keywords: Altitude; Bacterial response; Photodegradation; Terrestrial DOM; Trophic state