Abstract:

Freshwater ecological investigations on the community structure of phytoplankton in the Ganjiang River Basin were conducted three times during the year of 2009~2010.A total of 312 species (including varietas and modifications) were identified,belonging to 109 genera of 8 phyla,i.e. Chlorophyta,Bacillariophyta,Cyanophyta,Euglenophyta,Dinophyta,Cryptophyta,Xanthophyta and Chrysophyta.Bacillariophyta and Chlorophyta were the dominant phyla according to both index of species numbers and population density in the Ganjiang River Basin.All phytoplankton species identified were classified into 32 functional groups in the Ganjiang River Basin and finally a feature table of functional groups was built based on the phytoplankton habitat,tolerances and sensitivities.Groups F(〖WTBX〗Hormidium〖WTBZ〗 sp.),J(〖WTBX〗Scenedesmus quadricauda〖WTBZ〗),LO(〖WTBX〗Merismopedia tenuissima〖WTBZ〗),MP(〖WTBX〗Navicula〖WTBZ〗 sp.) & S1 (〖WTBX〗Phormidium tenue〖WTBZ〗) dominated the phytoplankton community during highwater period in the Ganjiang River Basin.Groups LO(〖WTBX〗Merismopedia tenuissima〖WTBZ〗),S1(〖WTBX〗Phormidium tenue〖WTBZ〗) & X2 (〖WTBX〗Chroomonas caudata〖WTBZ〗) dominated the lowwater period.Groups C(〖WTBX〗Cyclotella meneghiniana〖WTBZ〗),J (〖WTBX〗Scenedesmus quadricauda〖WTBZ〗) & MP(〖WTBX〗Navicula simples〖WTBZ〗) dominated the normalwater period.This work is conducted firstly to classify the phytoplankton functional groups in large rivers of China,according to the classification method.Results showed that the functional groups,dominant in species numbers and population density in the Ganjiang River Basin,always live in mesotrophiceutrophic waterbody,suggesting that the aquatic surroundings of the Ganjiang River has been artificially interrupted at certain degree and the river is on eutrophication.Classification of the functional groups is a useful tool for understanding the phytoplankton community.However,it is necessary to check whether the grouping of species reflected the autoecological features of organisms