Preliminary Study On Swamp Of Desmids In Great Xing'an Mountains

Great Xing'an Mountains is located in northeastern Mongolia Autonomous Region and northeast and north of the autonomous region in Heilongjiang Province,which is one of the Chinese most comprehensive distribution of marsh type and concentration regions. Desmids are freshwater algae, only a few species are known to occur in brackish water. Great Xing'an Mountains is one of the regions where swamps is broad but concentrated. The swamp is one of the richest environments which algae grow in,especially desmids.The paper embodies the results of an extensive study on the green algae collected from various in the Great Xing'an Mountains in 2004-2009. Desmids is a unique group, which includes Mesotaniaceae and Desmidiaceae of Zygnematales. However,not all fresh waters accommodate a rich desmid flora.Great Xing'an Mountains generally is considered to harbor an extraordinarily diverse flora and fauna.Since 2005,a large number of biologists have investigated biodiversity in the area as part of the All Taxa Biodiversity Inventory.Many desmid species occur in various aquatic and subaerial habitates throughout the area and their diversity is summarized in the present study,A total 128 desmid taxa (species,varieties and forms) )belonging to two subgroups 20 genera have been found in the area since the first study published in 2007.The present study enhances the most recent published species list (Qin Na,2007) by 67 additional taxa.In addition to new records for the DXAC,19 taxa is described as new.They are: Cosmarium pachydermum var. incrassatum Scott et Gr?nlad, C. perforatum Lundell, C. protractum (N?g.) De Bary, C. striolatum (N?geli) W. Archer, C. regnellii var. chondrophorum Skuja, C. phaseolus var. subquadratum (West) Krieger et. Gerloff, C. isthmochondrum var. decussiferum (Borge) Croasdale, C. entochondrum West et West , Staurastrum denticulatum (N?g) Archer, S. furcigerum var. armigera (Bréb) Nordstedt, S. mucronatum Ralfs, S. longispinum (Bailey) Archer, S. curviostrum Turner, S. polytrichum(Perty)Rabenh, S. arctiscon var. glabrum West et. West, Staurodesmus insignis,Std. mucronatum Ralfs, Arthrodesmus convergens var. incrassatus Gutwinski, A. Phimus Turner, Hyalotheca dissiliens var. tatrica Raciborski, Euastrum pectinatum var. rostratum (Tayler) Krieger, Mesotaenium degreyi W. B. Turner.ect. According to the numbers of species, Cosmarium is the most, it includes 73 classification units, which accounts for 37.4% of the total; then follows Staurastrum, it includes 38 classification units, which appropriately accounts for 19.5%; the next is Closterium , it includes 23 classification units, which accounts for 11.7%; the other 19 genus includes 61 classification units which accounts for 31.3%. This paper made a preliminary identification and carried out some simple analyses on the species composition and the ecological characteristics of desmids from the collection site mentioned above. Being influenced by the topographical, geological, limnological and meteorogical conditions in various parts of the Great Xing'an Mountains, the desmids there shows the following distribution patterns: Desmids are found in various habiates and therefore several sample methods were used to collect them.In subaerial habitates,collections were done by scraping the organic material(algae and cyanobacterial biofilm) off the rock surface using a spoon with sharpened edges or a knife. The samples were stored in sizes of plastic flasks,depending on the character and size of the sample.A portion of each sample was preserved in 4% formaldehyde to maintain the cell strcture for later examination. Current classification of the desmids is primarily based on cell wall structures that often are only visible with help of an electron microscope.Distinctly poor in desmids are, e.g.,ponds,lakes and canals which are so rich in nutrients that the water is troubled by mass development of unicellular chlorococcaleans,blue greens or diatoms. At high nutrient levels (eutrophic waters) those algae will outcompete desmids which generally are marked by a lower intrinsic growth rate. Consequently,a high desmid species diversity is only to be expected in nutrient-poor (oligotrophic),clear waters.1,In this area, the diversities and species and distribution characteristics of desmids weren't totaly affected by factors such as regional climate or geographic location etc., it mostly depend on the microenvironment which it belongs to,thus different habits have different species.Besides, major desmids grow in swamp,species in other habits are relatively less.2,Based upon the maked regional differences both in number and in character among the desmids species collected,the flora of these plants in Great Xing'an Mountains may be divided into some groups, correspongding to the following regions. In these regions, the desmids have great varieties, the lower repetitiveness in different habits, comparatively high diversities.3,The most favourable season for collecting desmids is in summer-time as the population density of most species is at its highest.4,In macrophte vegetation and in desmid assemblies more or less regular combinations of species occur, linked up with a given habitat.Although desmids is the richest species in the Chlorophyta, so far only a few people is engaged in desmids classification.Therefore, this thesis firstly carried out a preliminary study on desmids in swamp areas of Arxan in Inner Mongolia, in order to provide a few fundamental materials to the investigation of desmids resources in our country.