Water quality characteristics of Poyang Lake, China, in response to changes in the water level

Abstract

As one of the fewremaining lakes that are freely connectedwith the Yangtze River, Poyang Lake exhibits large annualwater level (WL) fluctuations. In this study, weekly samples were collected at the north end of Poyang Lake from September 2011 to December 2012, and we investigated the mechanism of limnological responses to fluctuations in the WL. The study covers three seasons that were associated with WL fluctuations ranging from 8 to 19 m. Spearman's rank correlations and multivariate non-metric multidimensional scaling analyses indicated that low and high WL periods differed in a number of water quality characteristics. The low WL period coincided with the non-growing season and was associated with the peak concentrations of nitrogen, the highest turbidity (Turb), and the lowestwater temperature. The highWL periodwasmainly characterized by enhanced chlorophyll a concentration. Spearman's rank correlations revealed positive relationships between theWL and the concentrations of NO3-N and PO4-P and negative relationships between the WL and the Turb, total nitrogen, total phosphorus, NO2-N, and NH4-N concentrations. All results support the conclusion that the largeWL fluctuations are the principal drivers for physicochemical variables in this floodplain lake ecosystem.