Taxonomic Study Of Diatoms In Linzhi And Lasa Areas Of Tibet,China

Diatom is a tiny cell or group of eukaryotic algae.It is very easy to recognize,because of it has unique siliceous cell walls.The cell wall of diatom is composed of silica and pectin.It is consists of two valves,which form the valve and the girdle valve.Diatom distribution is very extensive,including fresh water,sea water and brackish water.Diatoms exist in hot springs with high temperature,temperature frigid zones,icebergs and poles.They even have traces of activity in moist soil,rock,aquatic plants and mosses.The influence of diatoms on the earth is huge and far-reaching,and they played a very important role in the ecological environment.We collected 129 specimens of diatoms from Linzhi and Lasa of Tibet in July 2015.The altitude,longitude,latitude,pH and water temperature were measured,and we recorded the collection sites,habitat and date in detail.The species of diatoms were observed,identified and described,and we analyzed their community structure and diversity of diatoms.The main results are as follows:1.In this paper,a classification system of Round et al.(1990)was used to identify diatoms in Linzhi and Lasa of Tibet.230 diatoms sample were identified,belonging to 3 classes,13 order,26 families and 62 genera.There are 10 new records in China.In this paper,the morphological description of all the species of diatoms observed were described,with light microscope photographs.2.The species diversity of diatom is high,the number of genera is large and 61 genera are observed.Coscinodiscophyceae has 5 genera and 6 species.Fragilariophyceae has 11 genera and 24 species.The other 46 genera and 200 species belonged to Bacillariophyceae.Among them,Gomphonema have 26 species,the most species,Cymbella has 20 species Navicula have 18 species,Cymbopleura have 12 species,Nitzschia and Pinnularia each has 11 species,accounting for 43% of the total species.3.There are three types of community types of diatom plants in Linzhi and Lasa of Tibet.Benthic habitats: mainly for stream benthic and river bottom habitat,pH 8.0-10.4,and water temperature is 4.1-22.2 ?;Adherent habitat: mainly for the grass,grass,rock,spirogyra,moss,pH 7.9-10.8,the water temperature is 3.8-32.6 ?;Floating type habitat: mainly for lakes,streams,rivers and wetlands,pH 7.7-8.9,4.1-22.3 ?.4.We analysis diatoms plant species diversity of Ranwu lake,Galang lake,Yangzhuoyongcuo and Lalu wetland.We used Shannon-Weaver diversity index H,Simpson index D,Margalef diversity index D,Pielou evenness index J,the diatom species composition and community structure to evaluate water.According to the diversity index evaluation result,Lalu wetland is in a good water quality,water quality is clean;water quality have mild pollution phenomenon in Galang lake,Ranwu lake and Yangzhuoyongcuo.