Diatom taxa and assemblages for establishing nutrient criteria of lakes with anthropogenic hydrologic alteration |
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| Institution: | 1. Centre for Research on Environmental Ecology and Fish Nutrient of the Ministry of Agriculture, Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China;2. Department of Bioscience, Aarhus University, Silkeborg 8600, Denmark;3. Sino-Danish Centre for Education and Research (SDC), University of Chinese Academy of Sciences, Beijing 100049, China;4. Museum of Natural History and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA;1. CAS Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;2. Department of Earth Science, Graduate School of Science, Tohoku University, Sendai 980–8578, Japan;3. Department of Botany, National Museum of Nature and Science, Amakubo 4–1–1, Tsukuba 305–0005, Japan |
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| Abstract: | Stressor-response models offer guidance for concentration-based nutrient criteria in lakes under human intervention. Diatom-based statistics from biological responses were incorporated to derive taxon-specific and community-level change points (thresholds) of phosphorous and nitrogen in 77 Yangtze floodplain lakes. Diatom metrics relating with conductivity were adopted as response variables, since conductivity explained the maximum variation (38.1%) in diatom assemblages via Bootstrapped regression trees. Nonparametric change-point analysis and Threshold Indicator Taxa ANalysis showed threshold responses of diatom community structure at 0.05–0.08 mg TP/L in connected lakes and 0.02–0.04 mg TP/L in isolated lakes. Distinct community change points of sensitive diatoms occurred at 0.96–1.63 mg TN/L in connected lakes and 0.52–0.63 mg TN/L in isolated lakes. Diatom community structures of tolerant taxa were substantially altered beyond 0.22–0.23 mg/L in connected lakes and 0.52–0.69 mg NOx/L in isolated lakes. Hydrological river-lake connectivity differed significantly in ecological nutrient criteria with more TN/TP criteria and less NOx criteria in connected lakes. Given the ecological significance and biological integrity, diatom-based statistics can provide more reliable change points (thresholds) for nutrient criteria than Chl a-nutrient relationships. |
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| Keywords: | Phosphorus Nitrogen Diatoms Nutrient criteria Hydrological connectivity |
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