Diversity Of Diatom Based On High Throughput Sequencing And Mophological Identification In Fengxian Section Of Jialing River

The Jialing River is one of the eight major tributaries of the Yangtze River with the great water flow,the large drainage area and the abundant natural resources.There have been many studies of the plankton in the lower-middle Jialing River,but the research about diatom resources in Fengxian section of Jialing River is still seldom.In this thesis,the diversity of diatom in Fengxian section of Jialing River was studied by using high throughput sequencing and morphological identification methods,and statistical analysis was also employed.The results showed that there were total of 73 taxa of diatoms including 67 taxa belonging to 7 families and 17 genera identified by scanning electron microscopy,34 species and 14 varieties identified accurately,but there were still 25 taxa which could not be identified to species.And there were 109 taxa of diatoms identified by high throughput sequencing method,in which 7 family 20 genera and 19 species were accurately identified.At family level,the results of high throughput sequencing and morphological identification method were consistent.Both of them contain 7 families including Coscinodiscaceae,Fragilariaceae,Achnanthaceae,Gomphonemaceae,Cymbellaceae,Naviculaceae and Nitzschiaceae.At genus level,there were 11 genera identified by high throughput sequencing,also by morphological identification,such as Melosira,Diatoma,Encyonema,Navicula,Nitzschia,et al.At species level,Melosira varians,Cyclotella meneghiniana,Synedra ulna,Cymbella affinis and Navicula pupula were identified by both methods.There also were other 6 genera belonging to Cymbellaceae,Naviculaceae,Coscinodiscaceae and Achnanthaceae identified by morphological identification.And there also had other 9 genera identified by high throughput sequencing,in which 4 genera belonged to Naviculaceae.At species level,there were significant difference between the results of high throughput seqencing and morphological identification.Excepting the species identified by both methods,there were 14 species identified by high throughput sequencing and 43 species identified by morphological identification.It indicated that the high throughput sequencing method was suitable for identification of diatom at genus level,and morphological identification method had an advantage at species level.The samples A5?B2?C11 which were collected in Fengxian section of Jialing River were statistically analyzed based on the result of morphological identification.The results indicated that dominant species quantity,diatom species and density were increased with altitude decreasing.The water quality was evaluated by using biological indicator.The results showed that the water quality of A5 was considered as ? mesosaprobic type,and B2,C11 were approaching to ? mesosaprobic type.The result of the Margalaef index was similar to biological indicator method.It indicated that three samples suffered different degrees of contamination.GI values indicated that water quality of A5 was the best in collected samples.The diversity index of Shannon-Weaver and Simpson showed that all the collected samples were in oligosaprobic zone.