Succession of phytoplankton in a shallow lake under the alternating influence of runoff and reverse water transfer

Abstract

Both runoff and water diversion can interfere with the physical and chemical environment of a lake and affect aquatic organisms. In this study, previously obtained data were used to analyze the phytoplankton community, water quality, water level, and temperature in Dongping Lake (DPH) before, during, and after the water diversion caused by the South-to-North Water Transfer Project. The results showed that the total density and diversity index of phytoplankton decreased in the water transfer period, and was related to low temperature. Temperature also affected the recovery of phytoplankton community structure when the water transfer period ended. In a water transfer cycle, changes in dominant genera were more drastic than that of a whole phytoplankton community, and dominant genera were sensitive to total phosphorus (TP) and total nitrogen (TN) changes. Water transfer alleviated the deterioration of water quality in DPH, but water transfer process increased the risk of water pollution. Runoff from Dawen River carried TN, TP, and chemical oxygen demand (COD) into DPH in the rainy season, which indirectly affected phytoplankton, while it also carried phytoplankton directly into DPH. Overall, these findings provide a clear understanding of the impact of water transfer projects on ecology in shallow lakes. HIGHLIGHTS Dominant genera change greater than genera in a whole phytoplankton community.; Reverse water transfer and runoff affect phytoplankton community alternately.; There is a risk of water quality deterioration during the water transfer process.; Runoff transfers water, pollutants and phytoplankton to the lakes.;

Keywords

• dongping lake
• phytoplankton community
• reverse water transfer
• runoff
• shallow lake
• the south-to-north water transfer project