武汉东湖后湖区浮游甲壳动物群落结构的研究

STUDIES ON THE STRUCTURE OF CRUSTACEAN ZOOPLANKTON IN HOUHU REGION OF LAKE DONGHU, WUHAN

武汉东湖后湖湖区浮游甲壳动物群落结构从 6 0年代至 90年代发生了十分显著的变化。浮游甲壳动物的物种丰度下降非常明显 ,枝角类的种类数从 6 0年代的 47种下降至 90年代的 1 7种 ,桡足类的种类数由 6 0年代的 1 4种下降为 90年代的 9种。 6 0年代枝角类的优势种隆线一亚种在 90年代被短尾秀体所取代 ,6 0年代的两种优势哲水蚤——长江新镖水蚤与特异荡镖水蚤的优势在 90年代消失 ,而 6 0年代很少的一种剑水蚤——台湾温剑水蚤在90年代跃升为优势种。随着滤食性鱼类密度的上升 ,枝角类的密度从 6 0年代至 90年代显著下降。哲水蚤 1 997及 1 998年的密度明显低于 6 0年代的密度。研究表明 ,浮游甲壳动物群落物种丰度的下降与后湖湖区沉水植被的退化有关 ,而优势种的演替主要受滤食性鱼类密度的影响。

Remarkable changes in the structure of crustacean zooplankton took place in the Houhu region of Lake Donghu from the 1960s to 1990s: species numbers of cladocerans and copepods decreased from 47 to 17 and from 14 to 9, respectively. During this period, the dominant cladoceran Daphnia carinata ssp. was replaced by Diaphosoma brachyurum, population of Thermocyclops taihokuensis increased rapidly, while the calanoid Neodiaptomus yantsekiangensis and Neutroditapomus incongruens became very rare. With increased filter feeding fishes in the lake, the densities of cladocerans and calanoids decreased remarkably. The present result indicates that the decrease in species richness of crustacean zooplankton in Houhu region was mainly related to degradation of submersed vegetation, while the replacement of dominant crustacean species was mainly influenced by the changes in density of filter feeding fish.