长江中游两个湖泊沉积物中枝角类微化石密度的垂直变化研究

湖泊沉积物中保存的枝角类微化石不仅能够重建湖泊枝角类的群落演替历史，还能反映人类活动的干扰强度。本文研究了龙感湖、武昌湖沉积物中枝角类微化石组成、密度垂直变化以及人类活动干扰对其影响。结果表明：在龙感湖和武昌湖沉积物中，分别鉴定出9种和12种枝角类卵鞍。龙感湖沉积物中的枝角类总卵鞍密度（LG1: 2.22 ind./(g·dw)；LG2: 2.57 ind./(g·dw)）高于武昌湖（1.63 ind./(g·dw)，象鼻溞壳刺的平均密度（LG1: 360.53 ind./(g·dw)；LG2: 558.26 ind./(g·dw)）显著高于武昌湖（1.52 ind./(g·dw)）。自20世纪60年代以来，武昌湖沉积物中枝角类的优势类群由裸腹溞属、尖额溞属种类向裸腹溞属、盘肠溞属种类转变。龙感湖在1950年前，枝角类卵鞍的优势种群为盘肠溞属种类；而1950以后，其优势类群由盘肠溞属、裸腹溞属种类向象鼻溞属种类转变。两个湖泊沉积物中枝角类卵鞍和象鼻溞壳刺密度的垂直变化与湖泊富养化过程和渔业养殖历史相一致。结果表明，人类活动的干扰强度影响了长江中下游湖泊沉积物中枝角类微化石的组成和密度变化。

The verticle variation on the density of cladoceran microfossils in the sediments of two lakes located in the middle reaches of the Yangtze River

Cladocera fossils preserved in lake sediments can reconstruct the community succession history of cladocera, and also reflect the disturbance intensity of human activities. In this study, the vertical changes of composition and density of cladoceran remains in the sediments of two lakes (Lake Longgan and Lake Wuchang) were studied, and the effects of anthropogenic disturbance on cladoceran composition and density were also discussed. The results showed that 9 species and 12 species of cladoceran ephippia were identified in Lake Longgan and Lake Wuchang, respectively. Total density of cladoceran ephippia (LG1: 2.22 ind./(g·dw); LG2: 2.57 ind./(g·dw)) in Lake Longgan was higher than in Lake Wuchang (1.63 ind./(g·dw)), and the density of Bosmina spine (LG1: 360.53 ind./(g·dw); LG2: 558.26 ind./(g·dw)) was significantly higher than in Lake Wuchang (1.52 ind./(g·dw)). Since the 1960s, the dominant cladocerans have varied from Moina spp. and Alona sp. to Moina spp. and Chydorus sp. in the sediments of Lake Wuchang. However, the dominant cladoceran was Chydorus sp. before 1950 whereas the dominant species changed from Chydorus sp. and Moina spp. to Bosmina sp. after 1950 in Lake Longgan. The vertical changes of the density of cladoceran ephippia and Bosmina spine in two lakes were consistent with the process of eutrophication and fishery culture history. Our results indicated that the anthropogenic interference levels influenced the composition and density of cladoceran remains in lake sediments located in the middle and lower reaches of the Yangtze River.