The ice cover shapes the spatial and temporal characteristics of water quality in Hulun Lake during winter

Abstract

Abstract Being the largest boreal steppe lake in Northeast China, Hulun Lake has been characterized by eutrophication induced by abnormally high organic matter. This work investigated therefore the physicochemical and water quality parameters of Hulun Lake, and that of the inflowing Crulen River and Orshen River through winter, to reveal the spatial and temporal characteristics of water quality without impact of algal bloom, atmospheric deposition, wind or allochthonous nutrient input. Results showed that the prevention of wind-induced sedimentary resuspension accompanied with the minimized volume of tributary inflows is supposed to predominate the eutrophication alleviation. The formation of ice cover had a slight concentrative effect on water ion content. However, ice cover resulted in an increasingly homogenous distribution of phosphorus and oxygen-depleting organic matter over the entire lake. The two headwater streams demonstrated limited impact on water quality in estuaries in winter without showing evident coordination in upstream water nutrient level. It is suggested that the prevention of wind disturbance by ice cover and the subsequently modified hydrodynamic and water ecological processes are the determinant factors on water quality in Hulun Lake during winter.