Dynamics of phytoplankton communities in the Jiangdong Reservoir of Jiulong River,Fujian,South China

Phytoplankton blooms occurring in the Jiangdong Reservoir of Jiulong River,Fujian Province,South China,are a potential source of contamination of the drinking water of Xiamen(Amoy)City.To understand the main factors governing phytoplankton composition and succession,we sampled phytoplankton and measured environmental parameters in the reservoir,weekly or biweekly from Jan.2010 to Feb.2012.We identifi ed 123 species of phytoplankton from 7 phyla and 74 genera.The major phyla were Chlorophyta,Bacillariophyta,Cryptophyta,Cyanophyta,and Dinophyta.The main trend in the succession of phytoplankton was from prevalence of Cryptophyta-Bacillariophyta communities to those of Chlorophyta-Cyanophyta.High cell concentrations of Cryptophyta,predominantly Komma caudate,Cryptomonas marssonii,and Cryptomonas erosa,were present in winter,associated with low river discharge and cold water.Bacillariophyta,primarily Cyclotella meneghiniana,Aulacoseira granulata,and Aulacoseira granulata var.angustissima,dominated in early spring,coinciding with high turbulence and low irradiance.During early summer and autumn,Chlorophyta,comprising Scenedesmus quadricauda,Dictyosphaerium ehrenbergianum,and Pandorina sp.were prevalent during conditions of warmer water temperatures and low turbulence.Cyanophyta,with dominance of Pseudanabaena mucicola,Merismopedia tenuissima and Raphidiopsis sp.increased throughout the summer,coinciding with higher water temperatures and lower nutrient concentrations.Dinophyta content was occasionally high during winter and summer.Peridiniopsis penardii(Dinophyta)bloomed during winter 2009,with a persistently high biomass recorded into early spring.Canonical correspondence analysis indicated that phytoplankton communities were infl uenced by river discharge,irradiance,water temperature,and nutrient concentrations.