[Effects of Hydrological and Meteorological Conditions on Diatom Proliferation in Reservoirs].

ABSTRACT

The proliferation of diatoms is an ecological disaster that harms the water quality of many reservoirs in China. In order to reveal the driving factors of abnormal algal blooms in reservoirs, phytoplankton community structure and the associated environmental factors from 2009 to 2016 from Shahe Reservoir in Tianmuhu were analyzed. Results showed that diatoms and there dominant genus were predominately driven by temperature, and the relationship between hydrology and nutrition was insignificant. Distinct relationships were recorded between different diatom genera and temperature over the past eight years. The optimum growth temperature of diatoms and Synedra were both 27℃, while that for Cyclotella and Achnanthes were both 19℃. Low temperature was suitable for the growth of Melosira, and its growth was compromised with increasing temperature. In a multivariable statistical analysis of the dominant diatom genus and the associated environmental factors, we found that the dominant diatom genus responded differently to the associated environmental factors. The total biomass of the diatom and the biomass of Synedra and Achnanthes were significantly and positively correlated with rainfall (P<0.05). The biomass of Cyclotella was significantly and positively correlated with total phosphorus, rainfall, and water level (P<0.05) and significantly and negatively correlated with water exchange rate (P<0.05). The biomass of Melosira was significantly and positively correlated with total phosphorus. The annual peak biomass of diatoms can be predicted by a multiple regression model with independent variables, including rainfall intensity, dissolved total phosphorus, and the accumulated temperature in winter and spring. Our results indicated that the proliferation of diatoms responds significantly to hydrological and meteorological factors while insignificantly to nitrogen and phosphorus loading. External load reduction is needed to maintain a good water quality in the reservoir. In addition, extreme weather conditions should be given attention to provide an early warning for diatom proliferation.