Phytoplankton Community And Biological Evaluation Of Water Quality In Changhu Lake

Changhu Lake is situated between the Yangtze and Han River, across the city of Jingzhou, Jingmen and Qianjiang.It is the third largest natural freshwater lake in Hubei Province, can be divided into Haizi Lake, Temple Lake, Matai Lake and the Great Lake region. This study is through a survey on the plankton community structure of Changhu Lake on July, October 2012 and January, April 2013, make use of the biodiversity indices, dominance index and other ways to get a primary analysis about the Changhu water quality, in order to know the current situation of Changhu water quality, provide a theoretical basis and scientific basis to keep the Changhu water environment well, the main findings are as follows:1. Structure of the phytoplanktonic communities(1) The phytoplankton were indentified belonging to 132 species, including 63 species of chlorophyta,30 species of bacillariophyta,19 species, of cyanophyta,8 species of euglenophyta,6 species of Xanthophyta,3 species of dinophyta,2 species of cryptophyta,1 specie of chrysophyta from the aquatic survey of Changhu Lake. There are abundant of phytoplankton in this aquatic, and mainly included chlorophyta (47.37%), bacillariophyta (21.05%), cyanophyta (14.29%) in the four seasons. The biomass account to 66 species in autumn as the largest number, in the spring the biomass is the least of 45 speices.(2) The abundance of phytoplankton in four seasons ranges from 30.6 X 105 ind./L to 675 X 105 ind./L.Among them, chlorophyta, bacillariophytad and cyanophyta are the highest, referring to the evaluation criteria of lake eutrophication, the Changhu Lake belongs to the level of mesotrophic state to moderately eutrophic state.(3)The dominant species of planktonic algae have 19 species, Including 7 species of cyanophyta,5 species of bacillariophyta,4 species of chlorophyta,2 species of euglenophyta,1 specie of cryptophyta. Chlorella Vulgaris is the dominant species live in the four seasons. The spring dominant species are 8, among them, the dominance index> 0.1 species include Cyclotella comta、chlorella vulgaris and chlorococcum infusionum. The summer dominant species are 8 too, only the dominance index of oscillatoria amphibian>0.1.The autumn dominant species are 12, both the chlorella vulgaris and chlorococcum infusionums dominance index >0.1.The winter dominant species are 4, the dominance index of cyclotella meneghiniana、synedra ulna and chlorella vulgaris>0.1.(4) The four seasons biodiversity indices of phytoplankton in Chanhu Lake ranges from 0.89 to 4.04. Evenness index ranges from 0.24 to 0.87.Richness index ranges from 0.13 to 2.03.the biodiversity indices and evenness index of autumn is higher, said that community structure is in a more complete and stable state, but another three seasons community structure could be more fragiler.The whole water quality of Changhu Lake is eutrophication or severe eutrophication.2. Structure of the zooplanktonic communities(1) In the investigation of Changhu Lake aquatic, there are 88 species of zooplankton have been indentified. Including 13 species of small-scale protozoa. 16.25% of the total zooplankton species; small-scale rotifer species are 42,52.50% of the total zooplankton species; Large-scalecladocerans species are 16, as 20%; Large-scale copepods species are 9, as 11.25%. Thecommunity structure feature is the proportion of Protozoa and rotifera is bigger than the cladocerans and copepods.(2) The seasonal abundance of zooplankton ranges from 5378.84ind.L-1 to 9554.17ind.L-1 and the average is 7280.33 ind.L-1. The figure in each season is: average abundance in summer rank first with 9554.17 ind.L-1, followed by autumn with 8353.32ind.L"’,data in winter ranks third with 5834.97ind.L-1,data in spring was the mini-mum(5378.84ind.L-1).The seasonal biomass of zooplankton ranges from 3.33 mg.L-1 to 13.33 mg.L-1 the average is 8.20mg.L-1.The data in each season ranks as following:summer ranks first with 13.33 mg.L-1, autumn ranks second withl2.24 mg.L-1, followed by spring with 3.90 mg.L-1,winter ranks last with 3.33 mg.L-1.The lake was in eutrophic state in autumn, while in moderate eutrophic to eutrophic state in other three seasons, among them about 58.33% of sampling sites were in eutrophic state. In all the four areas,eutrophic state in Haizihu area was more sever than that in the left areas (abundance and biomass in Haizihu area were more than 3mg.L-1,3000mg.L-respectively),followed by Mahongtai area and Yuanxinhu area.(3) There are 18 species of zooplanktonic dominant species the whole year (dominance index≥0.02), including 6 species of protozoa,they are actinophrys、 vorticella similis、strombidium viride stein、tintinnopsis wangi、tintinnopsis sinensis and halteria grandinella; 4 species of rotifera,they are polyarthra trigla ehrenberg、filinia major、asplanchna girodide guerne and keratella cochlearis; 4 species of cladocera, they are bosmina longirostris、simocephalus schoedle、daphnia carinata king、and moina micrura Kurz; 4 species of copepods, they are sinocalanusdorrii、paracyclops fimbriatus、nediaptomus schmackeri and mesocyclops pehpeiensis hu.Most the species of above belong to indicator species of moderate eutrophication. The annual dominant species Changed significantly.(4) The zooplanktonic annual biodiversity indices mean ranges from 1.02 to 3.31, Beta- moderately polluted is Majority. Evenness index ranges from 0.32 to 0.75.Belonging to light pollution or contamination in the state.Margalef index evenness ranges from 1.11 to 2.10, indicate Changhu Lake water quality is in Alpha-moderately polluted.The whole Changhu Lake water quality was in moderately eutrophic and eutrophic state.