Seasonal Variations Of Plankton Community And Its Water Quality Evaluation In Tianhe Reservoir Of The Daluo Mountain,Southern Zhejiang Province

Tianhe reservoir is located in Daluo mountain scenic area in Southern Zhejiang Province.Daluo mountain scenic area is located in the east of Wenzhou,bordering on Xianyan scenic area.The highest altitude of the peak is about 700 meters.It plays an ecological protection function for Wenzhou City with rich ecological and natural resources.In order to explore the association between plankton community structure and water quality of the Tianhe Reservoir,the plankton and physio-chemical factors in the Tianhe Reservoir were investigated and analyzed from February 2019 to January 2020.The results showed that,89 species of phytoplankton belonging to 60 genera and 7 phyla were identified in one-year survey period,and the annual average abundance and biomass of phytoplankton were 2.02×105 cells·L-1 and 0.26 mg·L-1,respectively.Bacillariophyta was dominant in the whole year,whereas the dominance in spring and autumn was Chlorophyta.Cyanophyta was shown to be the most abundant in summer.Cryptophyta appeared in autumn and winter,and both Euglenophyta and Pyrrophyta were distributed uniformly throughout the year with low abundances.The main annual phytoplankton species with higher dominance were Melosira granulata,Synedra acus,Navicula cryptocephala,Asterionella formosa,Pseudoanabaena,Closterlum venus,Pediastrum duplex,Peridinium bipes,Dinobryon cylindricum,Cryptomonas ovata.50 species of phytoplankton belonging to 23 genera and 4 phyla were identified in Tianhe reservoir,among which Rotifera had the most abundant species,i.e.,26 species.The annual average abundance of zooplankton was 2456 ind·L-1,and the species and abundance of rotifers were dominant.The annual average biomass of zooplankton was 7.39 mg·L-1,with the copepods accounting for the largest portion of 57.19%.The main zooplankton species with higher dominance in the whole survey year included Cyclops vicinus,Bosmina longirostris,Polyarthra trigla,Keratella cochlearis,Brachionus calyciflorus,Tintinnopsis sp..Redundancy analysis(RDA)showed that water temperature,total nitrogen、CODMn,and pH value were the main environmental factors influencing the phytoplankton community structure during the whole survey year.However,the environmental factors such as water temperature,nitrogen and phosphorus nutrients,DO,and pH value influenced the zooplankton community mainly.According to the analysis performed by combination of diversity indexes(including H’,J,M),plankton abundance,dominant species,and comprehensive trophic state index(TLI),the Tianhe Reservoir was evaluated as the trophic level between oligotrophication and mesotrophication.In conclusion,plankton community structure in the Tianhe reservoir of Daluo mountain exhibited obvious seasonal variation.The water quality of Tianhe reservoir is at a low to medium pollution level,when evaluated by the physical and chemical factors as well as biological indicators.The result also showed that,changes of plankton community structure can be used to denote the reservoir water quality,and this also provided the.basic data for the water ecological environment health evaluation of mountain reservoirs.