Distribution Pattern Of Periphytic Algae And Correlation To Its Environmental Factors In The Poyang Lake

Poyang Lake,located in the north of Jiangxi Province,is the largest freshwater shalllow lake with the characteristic of water carrying,throughput and seasonal variation in the Yangtze River Basin in China.The natural environment in Poyang Lake and its connected watershed was excellent.While,with the development of social economy,it is getting to experience problems such as increased environmental pollution and biodiversity declining.And so far,the background information of algae resources in the lake is lacking.As a type of periphytic organisms living on the matrix in waters,they are critical components of the food-chain and can provide matter and energy for aquatic ecosystems.Their variation in quantity and species can reflect changes of water quality and habitats.Therefore,it is of great ecological and social significance to study epiphytic algae in Poyang Lake.We collected periphytic algae from 183 sampling sites in Poyang Lake respectively in August 2017,November,February and May 2018.By studying species composition,distribution pattern and dominant species,the study aims to provide basic data for periphytic algae biodiversity and accumulate data for the establishment of database of periphytic algae resources in Poyang Lake.The relationship between periphytic algae and environmental factors was analyzed and the water quality of Poyang Lake was evaluated in order to discuss the function of periphytic algae in water quality assessment and monitoring.The main results were as follows:1.In this study,a total of 216 species of periphytic algae were recorded,belonging to 5 phyla and 101 genera.The species of Bacillariophyta was most abundant,with 162 species belonging to 60 genera,accounting for 75.00%;followed by Chlorophyta,with 27 genera 37 species,accounting for 17.13%;9 genera 12 species of Cyanophyta were detected,accounting for 5.56%;Euglenophyta and Dinophyta species respectively account for 1.85%(4 genera 4 species)and 0.46%(1genera 1 species).For the convenience of description,they were divided into threegroups: periphytic diatoms,filamentous algae and epiphytic algae.2.The number of species in different regions of Poyang Lake was quite different.In the lake,species richness was highest(157 species)in northern lake area,and lowest(116 species)in Sanjiangkou estuary area.In terms of the five rivers inflowing into the lake,species richness was highest in Fuhe river(108 species)and lowest in Xinjiang river(63 species).In lakes of surrounding rivers,the Dalianzi lake was abundant in species(94 species)while the Junshan Lake was fewer(63 species).3.Fourteen main dominant species of periphytic algae in the whole lake were determined: Melosira varians,Nitzschia palea,Cymbella tumida,Navicula symmetrica,Achnanthidium minutissimum,Aulacoseira granulata,Ulnaria ulna,Gomphonema lagenula,Gomphonema parvulum,Aerosakkonema funiform,Stigeoclonium spp.,Cladophora spp.,Oedogonium spp.and Spirogyra spp..Dominant species in lake area and surrounding waters were not much different.However,on different substrates,unique species were detected and there were certain differences in species composition.4.The water assessment results based on physical and chemical factors showed that the water quality of Poyang Lake was generally in the middle-light to slightly eutrophication,and some local areas were above the middle-eutrophication level;the water quality was best in the northern area,gradually worsening to the south,and the lakes in surrounding rivers were the worst.Water quality in summer and autumn was better than that in winter and spring.The water assessment results based on the biodiversity index were not exactly the same as those based on physical and chemical factor.However,the results of water quality evaluation based on different variables tend to be spatially consistent.Some dominant species can also indicate the water condition.The higher the relative abundance of Achnanthidium minutissimum was,the better the water quality was;The higher the relative abundance of Melosira varians,Nitzschia palea,Ulnaria ulna and Gomphonema parvulum were,the worse the water quality was.Our results showed the dominant species in filamentous algae cannot make effective evaluation indications for the water quality of Poyang Lake.5.Pearson correlation analysis indicated that several environmental factors such as water temperature,dissolved oxygen,p H,total nitrogen,total phosphorus,chemical oxygen demand and water transparency significantly correlated to the dominant species of diatoms.Redundancy analysis(RDA)showed that water temperature,dissolved oxygen content,velocity,conductivity,total nitrogen were themost important environmental factors affecting the distribution of diatoms in Poyang Lake.The results of two analytical methods were basically consistent,which verified some dominant species in periphytic diatoms can properly indicate water quality of Poyang Lake to some extent.