Effects of extreme water levels on nutrient dynamics in a large shallow eutrophic lake (Changhu Lake, China)

Changhu Lake, a large, shallow, eutrophic lake in central China, experienced an extremely low water level event from November 2015 to January 2016 followed by an extremely high water level event in July 2016. In this study, we examined the effects of two extreme water levels on the nutrient dynamics of Changhu Lake over five years. The nutrient parameters in Changhu Lake showed significant interannual variations, and the nutrient concentrations at the sites in the western part of Changhu Lake were 2-41% higher than those at the outlet of the lake. In late 2015, the effects of low water levels led to a 17-74% increase in nutrient concentrations. After July 2016, however, a high water level event occurred, leading to a 34-48% decrease in nutrient concentrations. These changes in nutrient parameters were strongly related to water level fluctuations (p