Comparative Study of the Blooms in Spring in Xiangxi Bay at Three Gorges Reservoir

Abstract

Frequent spring blooms have been observed in Xiangxi Bay (XXB) at Three Gorges Reservoir (TGR) since its initial filling. To identify the primary factor controlling spring blooms, in the spring of 2010 and 2011, a field monitoring plan was carried out in the area (XX) where serious blooms outbroke in XXB The environmental factors which includes Chlorophyll a (Chl-a), nutrients, water temperature, secchi depth, etc. were involved. According the comparative analysis on the environmental factors of spring 2010 and 2011 in XXB, We study the relationship between water temperature and Chl-a. The results show that the spring blooms in 2010 is earlier than that in 2011. Comparative analysis on water temperature in the two years showed that surface temperature in spring 2010 continued to rise earlier than in 2011, and also the time that surface temperature continued to rise is the same to the time Chl-a concentrations increased. When the total nitrogen (TN) concentrations decreased, relative water column stability increased, and the time that mixing depth (Zmix) decreased were the same to the time when the surface temperature continued to rise. While the Water temperature increased, utilization of algal on nutrient , promoted development of thermal stratification, Increase of relative water column stability, and the sudden decrease of mixing depth resulted in the blooms. Rising surface temperature continued to rise was one of the primary induction factors to the spring blooms in XXB.