三峡水库蓄水前后春季长江口鱼类浮游生物群落结构特征

 根据1999年、2001年、2004年和2007年春季长江口及其领近海域40个站位鱼类浮游生物拖网调查资料，采用相似性分析，探讨了长江口及其邻近海域春季鱼类浮游生物的组成、群落结构及生物多样性。分析结果表明：三峡水库蓄水后的2004年长江口春季鱼类浮游生物丰度迅速下降，仅为1999年的 13.9% 和2001年的 4.3% ，2007年略有回升；鱼类浮游生物群落结构年度间差异显著，2004年鱼类浮游生物群落结构与1999年和2001年相异性最高，鯷和凤鲚种群数量变动对其群落变异的贡献率最大，群落相似性以2004和2007年最高，达 71.17% ；与蓄水前相比，蓄水后的长江口鱼类浮游生物群落多样性也显著下降。

Ichthyoplankton Community Structure Characteristics during Spring in Yangtze River Estuary before and after Impoundment of Three Gorges Reservoir

Spatial and temporal variation of ichthyoplankton community structure before and after impoundment of Three Gorges Reservoir (TGR) in the Yangtze River estuary and adjacent sea area(30°45′-32°00′N, 121°00′-123°20′E) was analyzed based on the samples at 40 stations during spring of 1999,2001,2004 and 2007. Through the study, 39 species, consisting of freshwater, brackish, coastal and marine varieties, were collected in trawl nets. The ichthyoplankton abundance degree in 2004 rapidly was decreased with 13.9% of 1999 and 4.3% of 2001, respectively, and appreciably increased in 2007. The dominant species comprised Engraulis japonicus, Coilia mystus, Allanetta bleekeri, Trachidermus fasciatu and Chaeturichthys hexanema. The dominance of Engraulis japonicus and Coilia mystus was reduced in 2004. There was significant dissimilarity within four year’s ichthyoplankton community structure, and the dissimilarity in 2004 was higher, comparied with 1999 and 2001. Similarity of percentage analysis showed that Engraulis japonicus and Coilia mystus represented the highest contribution in the community structure variation. Moreover, the similiarity index of ichthyoplankton was highest between 2004 and 2007 with the value 71.17%; Ichthyoplankton community diversity before and after impoundment of TGR was significantly different in the Yangtze Rive estuary, and the diversity after impoundment evidently decreased. A series of environmental disturbances, which happened in the Yangtze River estuary and adjacent water during 1999-2007, directly or indirectly caused the variation of ichthyoplankton community structure.