Centennial blooming of anoxygenic phototrophic bacteria in Qinghai Lake linked to solar and monsoon activities during the last 18,000 years |
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| Authors: | Junfeng Ji William Balsam Ji Shen Man Wang Hongtao Wang Jun Chen |
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| Institution: | 1. Department of Geosciences, University of Arizona, Tucson, AZ, USA;2. Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, USA;3. College of Geographical Sciences, Fujian Normal University, Fujian 350007, China;4. Institute of Environmental Change, Xi''an Jiaotong University, Xi''an 710049, China;5. Department of Earth Sciences, University of Minnesota, Minneapolis, MN, USA;6. School of Anthropology, University of Arizona, Tucson, AZ, USA;7. College of Tourism and Geography, Yunnan Normal University, Kunming 650500, China;1. Key Laboratory of Alpine Ecology (LAE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China;2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100039, China;3. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China;4. Department of Hepatobiliary Surgery, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China;5. Department of Microbiology, Miami University, Oxford, OH 45056, USA;1. State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Science, Beijing 100012, China;2. Department Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506, United States of America;1. College of Earth and Environmental Sciences, MOE Key Laboratory of Western China''s Environmental System, Lanzhou University, Lanzhou 730000, China;2. National Research Center of Geoanalysis, Beijing 100037, China;3. Department of Geology and Environmental Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA;4. Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China;5. Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences, Institute of Tibetan Plateau Reseacrh, CAS, Beijing 100101, China |
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| Abstract: | The productivity of anoxygenic phototrophic bacteria (APB) can be inferred in the sediments of Qinghai Lake from the changing abundance of bacteriophaeophytin a (Bph-a). Using diffuse reflectance spectroscopy (DRS), we identified Bph-a in Qinghai Lake sediments from the late glacial period through the Holocene with a resolution of one sample every 30–50 years. The Bph-a profile of Qinghai Lake demonstrates that in the last 18,000 years APB were only present between 4.2 and 14 ka BP, a period of high rainfall and high summer solar insolation. All the APB blooming events correspond to times of enhanced freshwater influx as revealed by percent redness, an indicator of the input of iron oxide minerals. Our data suggest that solar insolation sets the stage for APB blooms, which are then promoted by increased summer monsoon rainfall and nutrients resulting in the development of a chemocline in the lake. The blooming of APB in Qinghai Lake appears as discrete centennial-scale APB events likely linked to solar activities. Our results suggest the presence of solar-induced, century-long, intense summer monsoon episodes in the middle and early Holocene and the late glacial period. |
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