EFFECTS OF NUTRIENT CONCENTRATIONS AND RATIOS ON THE EUTROPHICATION IN A MACROPHYTE-DOMINATED LAKE

摘要

Effects of nitrogen (N), phosphorus (P) and their ratios (N/P ratios) on the eutrophication in the Baiyangdian Lake, a macrophyte-dominated lake, were investigated based on long-term observation of water quality from 1991 to 2008. Nutrient inputs via the Fuhe River, the largest tributary, accelerated eutrophic process of the lake. The concentrations of total N and total P ascended annually and ranged in 10.26-36.60 mg/L and 0.89-3.07 mg/L, respectively. N/P ratios in the river varied from 10 to 17, which fitted the growth of macrophyte and made the reed dominated in the lake. The results indicated that N is the restricted factor of eutrophication and thus N removal from the river is essential to relieve eutrophication in the lake. In the case of high nutrient concentration, N/P ratios can be used to indicate the types of lake eutrophication.