Biological thresholds of nitrogen and phosphorus in a typical urban river system of the Yangtz delta, China

• DOI: 10.1016/j.envpol.2014.04.007
• Publication Date: 2014-05-01T00:15:41Z
• Authors: Xinqiang Liang; Sirui Zhu; Rongzhong Ye; Ru Guo; Chunyan Zhu; Chaodong Fu; Guangming Tian; Yingxu Chen
• Keywords: River delta

River health and associated risks are fundamentally dependent on the levels of the primary productivities, i.e., sestonic and benthic chlorophyll-a. We selected a typical urban river system of the Yangtz delta to investigate nutrient and non-nutrient responses of chlorophyll-a contents and to determine biological thresholds of N and P. Results showed the mean contents of sestonic and benthic chlorophyll-a across all sampling points reached 10.2 μg L(-1) and 149.3 mg m(-2). The self-organized mapping analysis suggested both chlorophyll-a contents clearly responded to measurements of N, P, and water temperature. Based on the chlorophyll-a criteria for fresh water and measured variables, we recommend the biological thresholds of N and P for our river system be set at 2.4 mg N L(-1) and 0.2 mg P L(-1), and these be used as initial nutrient reference values for local river managers to implement appropriate strategies to alleviate nutrient loads and trophic status.