Distributions Characteristics of Nutrients and Corresponding Ecological Effects in Dongting Lake

LIN Jie1, LI Bin2, CHEN Qian2,†

1. School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055; 2. Key Laboratory of Water and Sediment Sciences (MOE), Department of Environmental Engineering, Peking University, Beijing 100871; † Corresponding author, E-mail: qianchen@pku.edu.cn

Abstract Based on monitoring data of monthly average COD, TN, and TP concentrations at Chenglingji hydrological station in Dongting Lake from 1990 to 2015, the intra-annual variation, inter-annual variation patterns of nutrients in the water column of Dongting Lake were systematically studied by trend analysis, and further revealed their stoichiometric ratio characteristics and discussed the effects of nutrient concentrations and structure on algal growth. The findings showed that the intra-annual variation patterns of average COD, TN, and TP were similar, indicating that the nutrient content in dry season was higher than that in wet season. However, as for multi-year trend, the annual average COD, TN, and TP in Dongting Lake showed a significant increase since 1990, while C:N and C:P ratios decreased and N:P ratio increased over time. The average C:N:P ratio in the water column of Chenglingji station in Dongting Lake was 13:18:1, and redundancy analysis showed that nutrient concentrations and stoichiometry ratios in the water would affect algae growth, with C:N, C:P and COD playing a dominant role. During the study period, the overall nitrogen and phosphorus content of the water column in Chenglingji station was generally high and has already met the algae growth demand. In order to avoid adverse ecological consequences such as harmful algal bloom events, external nitrogen and phosphorus inputs should be controlled to maintain the stoichiometric ratio balance in the water column of Dongting Lake. Key words Dongting Lake; nutrient; stoichiometry; trend analysis