Seasonal Variation of Phytoplankton Communities in Xiangang Reservoir, a Tropical Shallow and High-yield Fishery Reservoir in South China*

Abstract

The Xiangang Reservoir is an important reservoir for drinking water supply in Guangdong,China.In order to understand seasonal dynamics of pelagic phytoplankton communities in the tropical shallow reservoirs with high fishery yield,phytoplankton,hydrological variables and water quality were investigated in the reservoir in 2008.The reservoir was eutrophic,the annual average concentrations of TN and TP were 0.83 mg L-1 and 0.046 mg L-1,respectively,and Chla ranged from 11.02 to 59.34 μg L-1.A total of 129 phytoplankton species were identifi ed.The species diversity was higher in flood season than in dry season.Chlorophyta was dominant,78 species in total was found,followed by Cyanophyta (25 species) and Bacillariophyta (16 species).The total phytoplankton abundance ranged from 0.16×108 to 7.49×108 cells L-1 and the total biomass from 0.63 to 5.09 mg L-1.The maximal abundance and biomass occurred in May and February,respectively,while the minimal abundance and biomass both in October.In general,the abundance of phytoplankton was higher in flood season than in dry season,but the biomass had an opposite pattern.Cyanophyta was the most dominant group in total abundance and Bacillariophyta was the most one in total biomass.Cylindrospermopsis sp.,Pseudoanabeana sp.,Limnthriox sp.,Aphanocapsa delicatissima and Dactylococcopsis rhaphidioides were the most abundant in distribution,and Cyclotella meneghiniana,Synedna ulna,Melosira granulata,Rhizosolenia longiseta,Achnanthes exigua,Aphanocapsa delicatissima,Pseudoanabeana sp.and Dactylococcopsis rhaphidioide were the most contributers of biomass.Statistically,TP,SD,inflows and precipication played the important roles in the seasonal succession of phytoplankton community in the Xiangang Reservoir.Fig 2,Tab 3,Ref 26