Study On Phytoplankton Community Structure And Analysis Of Correlations With Water Environmental Factors In Yao Lake

Yao Lake is the largest inland natural lake which sets aquaculture and entertainment as awhole in Nanchang, JiangXi province. Recently, water quality and eutrophication level have atendency to increase in the negative impact of human activities. In order to conductqualitative and the quantitative investigation to the phytoplankton, simultaneously carry onthe monitor and analysis to the corresponding water environmental factors, the researchestablished9monitoring points, and collected water samples separately in September andNovember2011,February,April and June2012.Using the monitoring dates analyzed thecharacteristics of the phytoplankton community structure and the space-time discipline, andevaluated the water quality by bio-diversity indexs, explored the relationship between thephytoplankton community structure and environmental factors by the Spearman rankcorrelation analysis, On the basis, using the grey relational analysis found the dominant factorfor changes of phytoplankton standing crop in each season, Through the results providereliable basis for protection of water resources, water environment management, pollutionprevention and decision-making in Yao lake. The main results included as follows:1．Toble of158species were identified, which belonged to70genera,8phyla. Amongthem, the species composition was dominated to Chlorophyta. Follow by Euglenophyta,Cyanophyta and Bacillariophyta. The species number of Cryptophyta, Pyrrhophyta,Chrysophyte and Xanthophyta was all low. The dominant species were predominantlyMerismopedia punctata Meyen, Dactylococcopsis sp.and Synechocystis sp. in Cyanophyta,Synedra acus Kützing, Melosira granulata var.angustissima O.Muller, Cyclotella sp. inBacillariophyta, Scenedesmus quadricauda（Turp.）Brébisson in Chlorophyta during thesurvey.2. The temporal and spatial variation of phytoplankton community structure manifestedsignificantly.The community structure of phytoplankton manifested significantly temporal andhorizontal characteristics. On the temporal variation as follow: the number of phytoplanktonspecies were most (126species) in the summer and at least (91species) in winter, and littlechange in the number of species in spring and autumn; The average of phytoplankton cellsdensity was49.95×10~5ind./L, a v-shaped variation,and the lowest in the winter(1.22×10~5ind/L), the highest in summer(363.27×10~5ind/L), which the cells density ofphytoplankton in the spring and summer growth significantly in2012; The dominant specieswere given priority to Cyanophyta, Chlorophyta and Bacillariophyta in autumn, Cyanophyta and Bacillariophyta in winter, Bacillariophyta in spring, and Cyanophyta in summer; Theaverage content of chlorophyll a (Chl.a) was35.97mg/m~3, presented high in spring, summerand autumn, the winter low (22.68mg/m~3). On the horizontal variation as follow: The numberof phytoplankton species is in north less than the south; The average of phytoplankton cellsdensity presented a rising trend from north to south; The dominant species changed in autumnand spring are not obvious, but change significantly in winter and summer among thedifferent monitoring sites; The Chlorophyll-a content in the south was higher,and the northwas lower; on the whole present a is higher, south north low; Q type cluster analysis showedthat gathering for the phytoplankton community structure was not the same in differentseasons, the aggregation is also slightly different in the same season.3. The temporal and spatial variation of biodiversity indexs for phytoplanktoncommunity structure was remarkable.The average of Shannon-Weiner index(H) was3.21,andPielou evenness index(J) was0.55. On the temporal variation, the change trend of H and J isbasically the same. According to the order of the seasonal average of H from large to smallwas: spring, winter, autumn, summer; J was: summer, spring, autumn, winter. On thehorizontal variation, H and J had a larger fluctuation in winter and summer than in autumnand spring. H and J were adopted to assess the water quality, The results indicated that theevaluation results were similar in autumn and spring, and the vast majority of monitoring sitesare light pollution or non-pollution; in winter, the water quality between light pollution andpollution on the whole. In summer, water quality between light pollution to heavy pollution,showing a worsening trend from north to south.4. The Spearman rank correlation analysis for phytoplankton cell density andchlorophyll-a content with environmental factors respectively showed that the environmentalfactors which affected the phytoplankton cell density were water temperature, pH, nitritenitrogen, chlorine and sodium, and the environmental factors which affected the content ofchlorophyll-a were transparency, suspended solids, salinity, permanganate index, nitritenitrogen, total phosphorus and soluble phosphate, turbidity, iron and manganese. Graycorrelation analysis between phytoplankton standing stock and environmental factorsindicated that the size of the correlation degree for phytoplankton cell density and Chl.acontent between the environmental factors were not the same in different seasons: thedominant factors ranking the first were pH and nitrite nitrogen in autumn (September2011);pH and manganese in autumn (November2011); nitrite nitrogen and manganese in winter(February2012); water temperature and permanganate index in spring (April2012); sodiumand permanganate index in summer(June2012).