蒙古高原北部Gun Nuur硅藻属种组成与分布特征

本文通过对蒙古高原北部表层沉积物中硅藻属种的鉴定,探讨硅藻属种的分布特征及对水环境变化的响应。Gun Nuur湖泊中共鉴定出2纲7科12属21种硅藻,以羽纹纲为主,Cymbella cistula、Amphora ovalis、Amphora baltica、Amphora ovalis var.pediculus等为相对优势种,且平均相对含量分别为24.4%、23.8%、16.9%、15.6%,其余属种均少于10.0%。优势硅藻种Cymbella cistula表明了Gun Nuur湖泊主要为淡水、偏碱性水体,pH值为8.0左右,距湖岸较近位置有大量的水生生物发育。Anomoeoneis costata和Anomoeoneis sphaerophora var.sphaerophora、Navicula oblonga反映出湖泊由于蒸发作用而导致水体咸化,湖泊矿化度升高,并且湖水属于Na-Ca/Cl-SO4型。在高纬度气候非常寒冷地区的湖泊中,硅藻生长受到严重的抑制作用。偏"胖"的特征有利于硅藻浮游以适应水体温度的变化,湖泊边沿结冰后向湖泊中心游动。湖泊在冰封后可以阻止风浪作用,并且在低于水温的季节中,冰封可以使湖泊水体在阳光照射条件下保持高于外部环境的温度而有利于硅藻的生长。广盐性、真静水性硅藻Epithemia intermedia反映了这种湖泊长期冰封下静水特征。

The Characteristics of Diatom Species and Their Distribution in Gun Nuur, Northern Mongolian Plateau

Diatom species from the surface sediments of the Gun Nuur in the north of the Mongolian Plateau were tested in order to discuss the distribution characteristics and their responses to water environment.The results showed that diatom species in the Gun Nuur include 2 classes, 7 families, 12 genera,and 21 species. Pennates is a predominant diatom species in this lake. The dominant species are Cymbella cistula, Amphora ovalis, Amphora baltica and Amphora ovalis var. pediculus, with the average percentages of 24.4%,23.8%,16.9%,15.6%, respectively, while all other species are no more than 10%. The predominant diatom species Cymbella cistula indicates that the Gun Nuur is a fresh water body with slight alkalinity(pH=8.0), and blooms a plenty of aquatic living organisms in the lakeshore. Diatoms Anomoeoneis costata, Anomoeoneis sphaerophora var. sphaerophora and, Navicula oblonga reflect that the lake waterbody is a Na-Ca/Cl-SO₄ type with an increasing tendency of water salinity and mineralization, which is caused by evaporation in the summer and autumn. The diatom species Anomoeoneis sphaerophora var. sphaerophora and Navicula oblonga indicate the feature that the water body is SO₄^2--rich. Under the extreme cold weather conditions, the growing of diatoms has been restrained. And the small and fat-liked diatoms will float in order to adapt to the temperature change. Under the ice-closed lake, the lake water is quiet with higher temperature than that in the open air in the sunshine days, which is good to the growth of diatoms. Meanwhile, the euryhaline and lenific diatom Epithemia intermedia can also be taken as evidence that the water body is static under the ice-closed lake.