Cyanobacteria In A Tributary Backwater Area In The Three Gorges Reservoir, China

The ecological processes leading to cyanobacterial dominance in reservoirs differ somewhat from those in lakes and rivers. To explore the development of cyanobacteria in response to large-scale reservoir operation, a 2-year, biweekly monitoring program was implemented from 2007 to 2009 in the Pengxi River Backwater Area, a typical tributary of the Yangtze River in the Three Gorges Reservoir. The data were divided into 3 subsets based on the seasonal operations of the reservoir. During the low-water operation period, temperature stratified in the water column, and intensive rainfall brought suspended solids and nutrients into the Pengxi River Backwater Area. These drivers led to relatively high levels of total particulate matter and low levels of euphotic depth in the water column compared with both the high-water operation period and reservoir discharge period. During these 2 periods, increases in water temperature stimulated the growth of most cyanobacteria. We concluded that the large-scale operation caused structurally different habitats in the Pengxi River Backwater Area, related to water depth, reservoir volume, and nutrient dynamics. These impacts were closely linked to seasonal effects, such as rainfall, river flow, and water temperature, which resulted in differences in habitat among reservoir operation stages.