西江两个广东鲂产卵场浮游植物群落差异分析

The study on community structure difference of phytoplankton in two Megalobrama hoffmanni spawning grounds of Xijiang River

2007年4月23～24日对西江两个天然广东鲂产卵场——青皮塘和罗旁的浮游植物种类组成及分布进行了调查,共发现浮游植物98种(含变种、变型和未知藻种),其中硅藻门(Bacillariophyta)70种,占总种数的71.43%;绿藻门(Chlorophyta)12属20种,占总种数的20.41%;蓝藻门(Cyanophyta)3属4种;裸藻门(Euglenophyta)2属2种;隐藻门(Cryptophyta)和金藻门(Chrysophyta)均为1种。两产卵场中,硅藻在浮游植物总密度中所占百分比均大于70%。青皮塘的浮游植物种类数和种群密度均呈自上游至下游增加的趋势;罗旁则相反。变异直链藻(M.varians)是两个产卵场共有的绝对优势种,根据该种的污染指示性作用,其在两个产卵场的分布差异在一定程度上或一个侧面反映出,罗旁的水质环境略优于青皮塘。

We studied the community structure and distribution of phytoplankton in two Megalobrama hoffmanni spawning ground （Qingpitang and Luopang） of Xijiang River. Total 98 species were identified, including 70 diatoms （contributing 71.43% to total）, 20 green algae （contributing 20.41% to total）; other species belong to Cyanophyta,Euglenophyta,Cryptophyta and Chrysophyta respectively. The phytoplankton density of Qingpitang and Luopang were 3.04~10,cells/dm3 and 2.71~104cells/dm3 respectively, and the contribution of diatom to total were both higher than 70%, which provided abundant food for Megalobrama hoffmanni and its juvenile fish. The species richness and population density of phytoplankton in Qingpitang increased from upstream to downstream, and the condition of Luopang was opposite, which maybe caused by different geographic position of two spawning grounds. Melosira varians was the dominant species of both two spawning grounds, and its different distribution at two spawning grounds indicated that the water environment of Luopang was better than Qingpitang.