青海湖硅藻组合及其季节变化——来自沉积物捕获器的初步研究

A brief assessment of diatom assemblages and seasonal dynamics in Lake Qinghai:a time-series sediment trap study

通过对青海湖捕获器中2010年7月至2011年10月份沉积物样品与青海湖湖岸7个地点表层样品的分析,获得青海湖现代硅藻组合及季节变化特征。捕获器沉积物样品中共鉴定出硅藻2纲32属56种,主要为咸水种与微成水种。其中,优势种为Berkeleya rutilans、Cocconeis placentula var.euglypta、Cyclotella choctawhatcheeana和Nitzschia inconspicua,此四种占总数的82%以上。硅藻组合变化具显著的季节性差异,冬季主要以浮游种Cyclotella choctawhatcheeana占优势;非冰封期则以附生种Berkeleya rutilans、Nitzschia inconspicua与Cocconeis placentula var.euglypta占优势。青海湖湖水具有高碱度,硅藻的保存率不高,其保存率具有夏季高、冬季低的季节性变化,但这不是造成硅藻组合显著季节性变化的主要原因,其季节性变化主要取决于水生植物的生长与湖区冰情。

Thirty sediment trap samples collected between July 2010 and October 2011 in Lake Qinghai and 21 modem samples collected in September 2012 offshore Lake Qinghai were analyzed for diatoms. Fifty-six diatom species belonging to 32 genera were identified. The diatom community was mainly composed of brackish species with a few freshwater species. Berkeleya rutilans, Cocconeis placentula var. euglypta, Cyclotella choctawhatcheeana and Nitzschia inconspicua were the dominant species, which accounted for more than 82% of the total diatom flux. Seasonal variation was distinct in the diatom assemblage succession. During winter, planktonic diatom Cyclotella choctawhatcheeana dominated in the trap samples, while epilithic and epiphytic species dominated during non-ice-covered period. However, on account of the high alkalinity in Lake Qinghai, dissolution of diatom is severe. Although the severity of dissolution also changed seasonally, as behaving as a high preservation in winter and low in summer, it was not the main factor driving the seasonal changes in diatom assemblage. We suggested that the seasonal variation in diatom assemblage might depend upon other factors, such as the growth of aqueous plant and ice cover.