The Spatio-Temporal Pattern Of Phytoplankton At Danjiangkou Reservoir

Danjiangkou Reservoir water source reserve as a national level and large artificial reserxoirs,has been received widespread attention.In order to explore the spatiotemporal variations in phytoplankton community and its influencing factors at Danjiangkou Reservoir,we conducted a one-year survey from May 2014 to April2015.Danjiangkou reservoir according to the basic shape feature set 24 sample point,investigation of danjiangkou reservoir distribution and water quality conditions of phytoplankton,laboratory analysis of phytoplankton species composition,dominant species,density and biomass of changes and changes of the water quality data in the month,the phytoplankton distribution changes in relation to environmental factors.In addition,through the distribution of phytoplankton and two reservoir water environmental factors to explore the relevance of the danjiangkou reservoir pattern of space and time.Reveals the main factors affecting the distribution of phytoplankton.The main research results are as follows:(1)During the investigation,a total of 7 Phylums,21 genera,38species of phytoplankton were collected.The phytoplankton community of was mainly composed of Chlorophyta(13genera,26species),Bacillariophyta(9genera,21species),Cyanophyta(8genera,9species),Pyrrophyta(3genera,3species),Cryptophyt(2genera,4sp ecies),Chrysophyta(1genera,1speicies).Scenedesmaceae bijuga,Cyclotella stelligera,Fragilaria intermedia and Melosira granulata were dominant species at Danjiangkou Reservoir.(2)The average biomass of phytoplankton is 0.35 mg/l,while the average density is 9.08×105 ind./L.Dominant species are Fragilaria spp.,Cyclotella spp.,Melosira spp.,and Scenedesmus spp..Fragilaria spp.is the dominant specie,and its average biomass is 0.089 mg/l making up 25.43% of total biomass.In recent years,high level of nutrient may be the main cause of increasement in Fragilaria biomassat Danjiangkou Reservoir.(3)Chlorophyta and cyanobacteria bloomed at summer,while diatom dominanted in spring,autumn and winter.(4)Total biomass of Han reservoir is greater than that of Dan reservoir.There was significant differences in phytoplankton composition between these two reservoirs.The dominant phylum of Dan reservoir is Bacillariophyta,while the dominant phylum of Han reservoir is Chlorophyta.(5)There was significant correlation between the biomass of phytoplankton and phosphorus,pH and dissolved oxygen(p<0.01).RDA analysis showed that the major environmental factors structuring phytoplankton community were dissolved oxygen,pH,phosphorus and temperature.For algae blooms preventing,strict measures should be taken to control the input of exogenous nutrient especially phosphorus.This study provides scientific basis for water quality improvement and control of eutrophication at Danjiangkou Reservoir.