Preliminary Study Of Biraphidinales Diatom From Guangxi Zhuang Autonomous Region(Chongzuo Region)

Guangxi Zhuang Autonomous region located in the South middle of China(20°54′-26°24′N,104°26′-112°04′E)belong to subtropical monsoon climate.The tropic of cancer crosses the central.Fresh water resource is rich in this area High diverse environment provide various habitats for aglae.Biraphidinales(Bacillariophyt,Pennata)is one of the largest groups of diatom,widly distributed and occupies important position in the evolution system of diatom Based on the classification scheme by Hustedt(1930)and Jin(1978),Biraphidinales belong to Pennata,include 3 families.But Round et al.(1990)modified the classification scheme based on the ultrastructure observed by SEM.We still use the name of Birahidinales for this big group,the classification of families and genus under this order are based on Round et al.(1990).Diatom samples were collected from Guangxi Zhuang Autonomous region in July 2014.We collected 100 diatom samples and made 200 slides.The samples were collected from streams,rivers,waterfalls,channels,etc.The pH value is between 4.78 to 9.16.Totally,118 taxa,belong to 14 families and 27 genera were identified.In this study,morphological characteristics of species were described.LM pictures were provide for every taxa,SEM pictures for some of the taxa were provide also.In the study,one new species of Neidium were observed.Both LM and SEM images are given in this paper.In our study,6 newly recorded species of China were observed,they are: Encyonopsis pfisteri Krammer、Oricymba voronkinae Krammer & Lange-Bertalot、Brachysira calcicola Lange-Bertalot、Frustulia magaliesmontana Cholnoky、Frustulia pangaeopsis Lange-Bertalot、Pinnularia saprophila Lange-Bertalot,Kobayasi & Krammer.The species composition and distribution of diatom in Guangxi were discussed preliminarily.The results are as follows:1.In Guangxi Zhuang Autonomous region,Biraphidinales diatom biodiversity is relatively abundant,but the quantity of each taxon are relatively low.2.Most of the taxa belong to Cymbellaceae,followed by Naviculaceae and Gomphonemaceae,only few taxa belong to Cavinulaceae and Sellaphoraceae.3.We compared the species composition and distribution of Biraphidinales from different environments and samples.Among the 4 types of habitats,the largest number of species appeared in the waterfall,followed by the less number of taxa from streams,canals and rivers.4.In 5 sampling sites which we observed,Detian waterfall、Fangcheng river、Blackwater river have the most abundant species,The second is Huangpao mountain and The Shiwan mountains.5.In addition,taxa which were widely distributed in all kinds of sites and habitats were rare.Dominant species are rare too.Only Gomphonema parvulum(Kützing)Kützing 、 Gomphonema hebridense Gregory 、 Gomphonema gracile Ehrenberg 、Stauroneis neocaledonica Manguin are the dominant species.