Spatio-temporal variation of algae and eutrophic status of Lake Zhelin, Jiangxi Province

Abstract

Lake Zhelin in Jiangxi Province is among the first batch of demonstrative lakes in the"High Quality and Healthy Lake Plan"initiated by Chinese government. To study its spatio-temporal variation of algae and water eutrophication status,sampling sites in both Lake Zhelin and rivers flow into it were investigated from August 2012 to July 2013. The results showed that Lake Zhelin belongs to mesotrophic waters,with average total nitrogen and phosphorus concentration 1 mg / L and 0. 05 mg / L,respectively. The development of algae in Lake Zhelin mainly shifted between cyanobacteria( Microcystis and Anabaena) in the summer and diatom( Melosira,Cyllotella and Synedra) in the winter. Cyanobacteria bloom happened in the west of the lake,with a much higher abundance than that in the east. There are three main drinking water sources in Lake Zhelin and one of them suffered from cyanobacterial bloom during summer. However,microcystin concentration in the drinking water was still far below the safety guideline 1 μg / L. The algae cell abundance in the three main rivers into Lake Zhelin was still low,and the algae cell abundance in Yangang River was near 1 × 107 cells / L in both summer and winter. The decrease of input water volume and water level in Lake Zhelin in dry seasons,stratification of the water column,low water transparency together with long retention time of the lake water were the main causes of the blooms in Lake Zhelin.