千岛湖水温垂直分布的季节演变对透明溞昼夜垂直迁移的影响

 千岛湖位于钱塘江上游新安江主流上,是中国北亚热带地区的大型深水水体,水温具有明显的分层现象,夏季出现温跃层。枝角类(Cladocera)是水库生态系统的重要类群,具有垂直分布及昼夜迁移的特性。为阐明枝角类垂直分布格局及昼夜迁移对水温垂直分布的生态响应,选择千岛湖坝前段超过60m水深的湖区于2004年9月至2005年8月按季节进行昼夜垂直分层采集,以透明溞(Daphnia hyaline)为对象开展相关研究。结果显示,透明溞是千岛湖坝前段湖区四季的优势种,基本以聚合的模式(MI>1)分布于垂直水柱中,春、夏、冬3季有正常迁移现象,秋季则无明显的昼夜垂直移动行为。千岛湖温跃层的出现加强了透明溞在垂直水柱中的聚集,促进了其夜间的上迁运动,使其成为坝前段湖区表底层水体物质交流的纽带。

Influence of Seasonal and Vertical Distribution of Water Column Temperature on the Diel Vertical Migration of Daphnia hyaline in Qiandao Lake

Qiandao Lake located in the upper reaches of Qiantang River is a large deepwater reservoir in north subtropical zone of China. In the lake, the water temperature reportedly has the vertical stratification phenomenon, and it presents thermocline in the summer. Cladocera is an important group in the reservoir ecosystem, it is generally recognized that Cladocera possesses the behaviors of vertical distribution and diel migration. Then the area next to the dam (with the total water depth exceed 60m) was selected as the sampling site, the environment factors and cladocerans species in vertical layers were analyzed in four seasons (from September 2004 to August 2005). The specie Daphnia hyaline was chosen as the main research object in order to clarify the influence of seasonal and vertical distribution of water column temperature on the vertical distribution pattern and diel migration of cladocerans in Qiandao Lake. The results show that D. hyaline is the dominate specie all year around, and essentially has an aggregated distribution pattern (MI>1) in water column, and with normal migration all year around except autumn. The thermocline in Qiandao Lake strengthens the aggregated distribution of D. hyaline in water column, promotes the upward-migration in the night. The fact makes the specie D. hyaline the important link between top and bottom waters for material interchange and energy flow.