武汉东湖浮游藻类物种多样性的研究

DIVERSITY OF THE PHYTOPLANKTON IN DONGHU LAKE,WUHAN

从 1994年 1月至 1996年 12月 ,每月定期从东湖四个常规采样站采集浮游藻类标本进行研究。经鉴定共发现 2 6 0个分类单位 ,隶属于 7个门的 99个属 ,其中有 2种为中国新记录。以 1995年浮游藻类的群落结构进行分析的结果是 :浮游藻类的种类数以绿藻门最多 ,硅藻门次之 ;各站基本上均以夏季种类最多 ,其次为秋季和春季 ,冬季最低 ;四个站中分布的种类差异不明显 ,各站都出现的种类数占全部种类数的 39.6 % ;不同的站或同一个站在不同的季节其优势类群亦不同。计算了与水体营养类型有关的浮游藻类群落的两种指标—多样性指数和硅藻商。对东湖浮游藻类群落结构的特征及变化与水质的关系进行了探讨 ,从浮游藻类群落的演替指出东湖的富营养化程度自2 0世纪 5 0年代以来一直在加剧。

The composition and diversity of phytoplankton community were analysed in four sample stations in Donghu Lake, Wuhan from Jan. 1994 to Dec. 1996. 260 taxa belonging to 99 genera and 7 phyla were observed, of which 2 taxa were recorded for the first time in China. The composition was similar in the four stations in successive years, and the community structure of the phytoplankton in 1995 were analyzed. The number of the total species was the highest in summer, minimum in winter and the species occurred at the four stations counted for 39.6% of the total species. The species number of Chlorophyta was the highest, with high species number of Chlorococcals found (counted for 80% of Chlorophyta), but none species was considered to be dominant species. The second highest species number was found to be Bacillariophyta, of which pennate diatoms comprised more than 80% of the diversity, with less than 20% centric diatoms found. However, two centric diatoms (Cyclotella meneghiniana and Stephanodiscus hantzschii)were detected to be dominant species. Though the species number of Cyanophyta was not high, the community was dominated by Cyanophyta in Summer and Autumn in four stations, dominant species included Merismopedia minima, Phormidium tenue and Oscillatoria limnetica. Cryptophyta could be dominant groups in winter or spring though only 3 species were identified. The dominant species in stations Ⅰ&Ⅱ are different from those at stations Ⅲ&Ⅳ in Winter and Spring: dominant speices in stations Ⅰ&Ⅱ are indicators of eutrophication, but some dominant species in stations Ⅲ&Ⅳ were β-mesotrophic indicators, e.g. Achnanthes minutissima. Three kinds of diversity index(Margalef, Simpson and Shannon-Weaner) were calculated and results suggested that diversity index might be not good indicators of water quality when the water was at high eutrophication status. However, the Diatom Quotient declined in the order of stations Ⅰ to Ⅳ and was proposed to be highly correlated to water quality. Finally, the relationship between changes of the phytoplankton community structure and the water quality was discussed. It is concluded that the eutrophication had been aggravated since 1950s.