Dynamics of water quality and phytoplankton community driving by extreme inflow in a huge drinking water source reservoir, China

The tail of reservoir is the un-stable zone in water quality and phytoplankton community. Therefore, it is the crucial zone in aquatic ecosystem transition. To understand the transition characteristics and driving mechanisms of water environment dynamics, eighteen months high frequent monitoring of water environment and phytoplankton community in tail of a deep and large reservoir, Xin'anjiang Reservoir in southeast of China, were undertaken by water quality monitoring buoy and 3-days interval water sampling. The result showed that, there are clearly seasonal thermal and oxygen stratification in the river mouth of the reservoir. The nutrient and chlorophyll-a concentrations also show stratifying phenomenon during thermal stratification period. Heavy rain and inflow will shortly destroy the stratification. Nutrient concentrations were high dynamic in the river mouth. Total phosphorus ranges among 0.011 mg·L^-1 to 0.188 mg·L^-1, and total nitrogen ranges among 0.75 mg·L^-1 to 2.76 mg·L^-1. The dissolved phosphorus occupied 56% of total phosphorus, and dissolved nitrogen occupied 88% of total nitrogen, respectively. Nutrient concentrations influenced strongly by rainfall intensity and inflow rate. Total phosphorus and nitrogen concentrations were significantly related to 3-days accumulated rainfall. Nutrient concentration in flood season (March to June) was significantly high than non-flood season (P