Distribution Characteristics And Ecological Habit Analysis Of Modern Diatom Of Lakes In North Tibet Plateau

Diatom is very sensitive to small changes of environmental factors for its simple cell structure and its relatively fixed habitat. The environmental changes, such as water ions, depth, total suspended solids(TDS), specific conductance(SC), temperature, nutrition, water disturbance and so on, all these changes will result in the changes of the population and distribution of diatom. In this paper, we study on the ecological characteristics of diatom and relationship between diatom and environmental factors, this work can supplement the data base of the relationship of diatom-environmental factors, but also promote to establish quantitative relationship between them, and provide the theoretical support.Tibet has the unique climate, varioius type lakes and a rich variety of diatoms species. Selecting the surface sediment and water samples of20lakes from Ali and Nagqu in Tibetan plateau and using the analysis method including the Detrended Correspondence Analysis, Principal Components Analysis and Contrastive Analysis, we discussed the composition and distribution and the ecological habit of diatom, the influence of environmental factors on diatom. The key conclusion included:(1) We identified212diatom species, include10families and27genera, Diatoms in the study main like to live in alkaline freshwater. Dominant genera are Navicula (17.45%), Nitzschia (10.85%), Cymbella (8.49%), Fragilaria (8.49%), Gomphonema (7.08%), Pinnularia (6.13%) and so on. Dominant species are Fragilaria pinnata, Denticula elegans, Cocconeis placentula, Amphora ovalis var. pediculus, Amphora veneta, Cymbella subcistula, Cymbella delicatula, Fragilaria brevistriata var. inflata, Fragilaria leptostauron var. martyi, Navicula cincta var.leptocephala, Navicula radiosa, Nitzschia denticula, Opephora martyi.(2) Water salinity is the major limited factor on diaom in Tibet, while, pH and nutrition also effect the growth and reproduction of diatom. On the other hand, diatom has obvious selectivity on Ca2+、Mg2+/Ca2+(3) Amphora ovalis var. pediculus growth well in water with pH=9.01, SC=0.344mS/cm; A. veneta grown prosperous when salinity is345.66mg/L and have high salt tolerance; Cocconeis placentula prefer the water with sulfate; Denticula elegans is rich in the condition with3.98mS/cm, its best pH range is8.70-8.90; Fragilaria leptostauron var. martyi has high salt resistance, and can grown in saline water with SC of3.980mS/cm; optimal growth range of pH and SC for Fragilaria pinnata is8.68and0.303mS/cm, it as well as F. pinnata and Navicula radiosa indicate low temperature environment; N. cinta var. leptocephala live in alkaline and freshwater environment; the most excellent growth range of pH for Nitzschia denticula is8.70-8.90; existence of Opephora martyi as dominate species indicates good nutrition environment.(4) Denticula elegans, Epithemia sorex, Nitzschia denticula indicate the environment features of high calcium, low Mg2+/Ca2+. Cocconeis placentula and Cymbella delicatula can indicate the clean environment, Fragilaria leptostauron var. martyi can stand for environment with silghtly polluted, Denticula elegans can adapt to the clean to slightly polluted water body, Fragiluria pinnata, Nitzschia denticula, Naviculacinta var. leptocephala and Navicula radiosa has a certain ability to endure polluted environment, but prefer to live in clean environment.