巢湖微囊藻和浮游甲壳动物昼夜垂直迁移的初步研究

2002年10月进行了巢湖微囊藻和几种优势浮游甲壳动物的昼夜垂直变化的研究,结果表明:微囊藻具有明显的昼夜垂直变化现象。白天上层水中的微囊藻密度显著高于下层水中,夜晚逐渐下沉使得下层水中的密度相对高于上层水。微囊藻与叶绿素a、水温、溶解氧和pH等均呈显著的正相关(p<0.01)。几种优势浮游甲壳动物的昼夜垂直迁移存在较大的差异。短尾秀体溞和角突网纹溞白天在下层水(1.5m和2.5m)中的密度较高,夜晚则倾向于在上层水(0m和0.5m)中活动。相反,卵形盘肠溞白天在上层水中密度较高,象鼻溞则在11:00和15:00时各水层中的密度显著高于夜晚。汤匙华哲水蚤和广布中剑水蚤白天倾向于在下层水中活动,夜晚则逐渐迁移到上层水中。许水蚤在夜晚和凌晨3:00时各水层中的密度显著高于白天。中华窄腹剑水蚤昼夜垂直变化不明显。微囊藻与短尾秀体溞密度呈显著的负相关,而与象鼻溞和卵形盘肠溞呈显著的正相关(p<0.01)。

Diel vertical migration of Microcystis and crustacean zooplankton in Lake Chaohu

Diel vertical migration of Microcystis and crustacean zooplankton were investigated in October 2002.The results showed: Diel vertical migration of Microcystis(predominant Microcystis aeruginosa) was obvious.The daily density of Microcystis in the upper layer was higher than in the lower layer,the reversed pattern was observed at night.Chlorophyll-a(chl-a) had a similar pattern.Positive correlations(p<0.01) of Microcystis were observed with chl-a,water temperature,DO and pH.Diel vertical migration of several dominantly crustacean zooplanktons was surveyed.For Diaphanosoma brachyurum and Ceriodaphnia cornuta,higher density occurred daily in the lower water layer(1.5 m and 2.5 m),while they migrated to the upper layer(0 m and 0.5 m) at night.On the contrary,higher density of Chydorus ovalis appeared daily at 0 m and 0.5 m.The density of Bosmina at 11:00 and 15:00 at different water layers was higher than at night.Sinocalanus dorrii and Mesocyclops leuckarti were daily inclined to concentrate on the lower layers while they migrated to the upper layers.The density of Schmackeria sp.in different water layers at night and at 03:00 was greatly higher than other sampling times.Diel vertical migration of Limnoithona sinensis was not obvious.The negative correlation(p<0.01) between Microcystis and the density of D.brachyurum was observed,while it was positive with Bosmina and C.ovalis.