The effects of the three Gorges Dam's (TGD's) experimental impoundment on the phytoplankton community in the Xiangxi River, China

The experimental impoundment of the Three Gorges Dam (TGD) on phytoplankton community was conducted in 2008. Before the impoundment, the phytoplankton comprised various taxa including Bacillariophyta, Chlorophyta, Cryptophyta, Dinophyta and Cyanophyta. While Chlorophyta contributed considerable taxa, numerically, diatom constituted the main component. Cell density was 1.83~7.78 × 106 ind/L: biomass was 3.62~8.89 μg/L; total phosphorus (TP) and total nitrogen (TN) were 0.101~0.233 mg/L and 1.367~2.596 mg/L, respectively. During the impoundment, some species disappeared, leaving diatom dominant. Cell density and biomass decreased significantly (p < 0.05) and pH and TP decreased; but, dissolved oxygen (DO) and TN increased. Remarkable spatial (horizontal and vertical) (p < 0.05) as well as temporal variations were recorded in the distribution of phytoplankton. Temporal effects included changes in the phytoplankton community and nutrient concentration due to dilution and enrichment by the inputting water. © 2010 Taylor & Francis.