Dynamics Of Water Quality And Plankton Communities In A Newly Constructed Reservoir: Feilaixia Reservoir, Guangdong Province

The hydrodynamics, nutrients and the plankton distribution in a newly constructed large reservoir: Feilaixia Reservoir in Guangdong Province were investigated from 2000 to 2005 . The hydrodynamics was characteristic of seasonal change in outflow, which varied from 130 to 3876m~3/s, was higher in flood seasons than in dry seasons. The water column was never stratified, and the lowest temperature in winter is not less 14℃.During the investigated period, the water level of the reservoir varied slightly from 20.6m to 24.1m, regulated by flooding control. The retention time was short, about two weeks in summer and two months in winter. Water transparency varied 0.4m to 5.5m, has a increase trend over last six years. The retention time and water transparency were significantly correlated with outflow (r=0.602 and r=0.534, respectively), The mean concentrations of TN in surface water ranged from 571.3μg/L to 3103μg/L, the mean concentrations of TP ranged from 4.1μg/L to 186.3μg/L, The nutrient concentration was higher in flood season than in dry season , and were inputed from feeding rivers. TP concentration was remarkably declined in 2001. The concentration of chlorophyll a in the surface water ranged from 0.67μg/L to 6.12μg/L. According to tophic state index based on TP, TN, SD and Chla, the reservoir was mesotrophic.In the reservoir, 156 species of phytoplankton was observed in the collected samples throughout the study periods, 28 species in Cyanophyta, 76 species in Chorophyta, 40 species in Bacillariophyta, 4 species in Pyrrophyta, 5 species in Chrysophyta, 3 species in Euglenophyta and 1 species in cryptophyta. The specific composition of phytoplankton was seasonally dynamic . The species richness was increased in the first three years and then became stable, there were about 50 to 70species in each sample. Compared to the other reservoirs with a long residence time, the abundance of phytoplankton was low in the Feilaixia reservoir, ranged from 2.6 × 10~4cells/L to 218.6 ×10~4cells/L, it was higher in flood season was higher than in dry season. Most of phytoplankton species greastest axial linear dimension(GALD) were range from 6.2μm to 126μm, The dominated species was Pseudoanabaena sp. and Melosira granulate with GALD >100 μm, the subdominated species was Cyclotella...