鲢和长刺溞与浮游植物相互作用关系研究

STUDY OF THE RELATIONSHIP OF SILVER CARP AND DAPHNIA LONG1SPINA WITH PHYTOPLANKTON

在营养物负荷和浮游植物密度较高的鱼池围隔条件下,接种长刺溞,长刺溞能稳定生长,达到并维持足够高的密度,有效地控制了浮游植物的过量生长;放养鲢鱼后,该微型生态系统的群落结构、营养水平又明显改变,长刺溞密度很快降低,原生动物和小型轮虫密度上升,浮游植物生物量起初有所减少,但很快又上升,而叶绿素a含量始终明显上升,说明鲢鱼的放养加速了浮游植物的生长繁殖,增加了浮游植物叶绿素a的含量。同时,鲢鱼的放养,显著地增加水体NH4+-N,TP含量。根据试验结果可认为,在一定条件下,通过生物操纵,减少或不放鲢鱼,保持足够的长刺溞密度,可以达到控制浮游植物过量生长,改善水质的目的。

In an experimental study of bio-manipulation of silver carp and Daphnia longispina under relatively high nutrient loading, D. longispina inoculated proved to be effective to control excessive growth of phytoplankton and substantially changed the community structure and nutrient levels of the microcosms stocked with silver carp, making them more eutrophic at the end of the experiment. It was detected that primary production was positively correlated with phytoplankton density and negatively with zoo-plankton density in microcosms. As Daphnia longispina density decreased, the density protozoa and miniature-type rotifera density increased. Chlorophyll a concentration rose steadily, suggesting that stocked silver carp facilitates then propagation of phytoplankton. Silver carp significantly increased TP, COD and NH4+ - N, suggesting that silver carp facilitates eutrophication on shallow waters. It is concluded that bio-manipulation is effective to control excessive phytoplankton growth and that introducing such mega-herbivorous zooplankton as Daphnia longispina into lakes and/or reducing grazing pressure of fish are favorable for achieving sufficient density of macrozooplankton.