Study On Biodiversity Of Diatom In The Poyang Lake

The species of diatoms are diverse,they are one type of unicellular eukaryotic algae with highly silicified cell walls,and they are widely distributed in different habitats.Diatoms are important primary producers in water bodies and can respond quickly to changes in the nutrient status of water bodies.They play an important role in the water ecosystem.Poyang Lake,as China's largest freshwater lake,is also the largest single-pass lake in the Yangtze River.Human activities have a strong influence on the natural ecosystem.At present,there is no specific report on the diatom diversity in this area.This thesis systematically studies the species composition and distribution of diatoms in the Poyang Lake and enriches the species diversity of diatoms in the Poyang Lake.It provides a scientific basis for the biodiversity conservation in the Poyang Lake.It is a basic data for "Biodiversity Survey and Assessment of Phytoplankton and periphyton in the Poyang Lake" project,and provide basic data for the country to establish a database of diatom resources in the Poyang Lake.In August 2017,October 2017,February 2018,and May 2018,we collected 66 samples in the Poyang Lake and its periphery.Light microscopy(LM)and scanning electron microscopy(SEM)were used to systematically identified the diatom species.The main results are as follows:1.A total of 72 genera 314 species(including varieties and forma)of diatoms were found in the Poyang Lake,including 1 new species,11 species(including varieties)of new records in China,and 210 species(including varieties)discovered in the Poyang Lake for the first time.This article describes the detailed morphological characteristics of all species,each species is described and are illustrated with light electron microscopy and some of them illustrated with scanning electron microscopy.1 new species were found in Poyang Lake: Surirella poyangense sp.nov.The new records in China are as follows: Eunotia camelus var.arcuata,Eunotia ewa,Eunotia vumbae,Eunotia yberai,Hippodonta rostrata,Pinnularia nordica,Placoneismolestissima,Placoneis potapovae,Sellaphora meridionalis,Sellaphora interrupta,Surirella bonsaensis.2.Species composition of diatoms in the Poyang Lake were summarized and analyzed,which is mainly Pennatae,with 60 genera and 288 species,accounting for91.7% of the total species.There are 26 species(belong to 12 genera)in Centricae,which account for 8.3% of the total species.Aulacoseira,Melosira,Discostella,Cyclotella,Cyclostephanos,Fragilaria,Ulnaria,Navicula,Cymbella,Encyonema,Gomphonema,Gyrosigma,Achnanthidium,Nitzschia,Surirella are dominant genera which account for 46.2 % of overall species.3.Since the water level fluctuations of Poyang Lake are mainly affected by the inflow of the five rivers and the Yangtze River,according to the water level,Poyang lake is divided into two types of habitats: lake and river.There is no significant difference in the dominant diatom species in these two habitats,and most of them are widely distributed freshwater species.Asterionella formosa collected in spring and winter(4.5-25 °C)was suitable for river,while Acanthoceras zachariasii in summer and autumn(15.5-35 °C)was adapted for Lake.The species composition of diatoms has changed slightly in different seasons,and Aulacoseira granulata(including varieties and forma)have become perennial dominant species.They are 225 species,181 species,176 species and 276 species of diatoms were observed in spring,summer,autumn and winter.It can be seen that the species of diatoms in the spring and winter are relatively abundant than those in the summer and autumn.4.We observed many widely distributed freshwater species: Aulacoseira granulata,Melosira varians,Discostella stelligera,Cyclotella meneghiniana,Navicula capitatoradiata,Gyrosigma acuminatum,Nitzschia palea,Surirella angusta and Cymatopleura solea.There are some pollution indicator species,such as Nitzschia palea,Ulnaria ulna,Cymatopleura solea,Navicula cryptocephala,Aulacoseira granulata,Gomphonema parvulum,Fragilaria crotonensis and Fallacia pygmaea.