河库两相水位波动对三峡水库库尾溪流底栖动物影响的生态机制研究

Water regime in riverine zone of the Three Gorges Reservoir (TGR) characterized by periodic change between ‘river’ and ‘reservoir’. Environmental factors, such as water quality, physical habitat and sediment transport, were variable here. As a result, structure and spatial-temporal patterns of stream benthic macroinvertebrate in the riverine zone was also extremely complex. However, the influence of water regime in riverine zone of reservoir on macroinvertebrate and its mechanism were little understood as few former researches focused on this topic. This research would choose Baijia Stream in Kaixiang County in Chongqing as study area. We aim to discover the influence of periodic water level fluctuation on stream macroinvertebrate in riverine zone of the TGR and explore the relationship between macroinvertebrate and environmental factors and the mechanism inside. We hope our research could supplement the sparse empirical database of the effect of periodic water level fluctuation of reservoir on stream macroinvertebrate and be useful to reservoir heath, sustainable management and biodiversity conservation of the TGR.

水库库尾溪流位于“河”与“库”的交错带，水文情势具有明显的河库两相交替变动特征。独特的水文情势对库尾溪流底栖动物产生巨大影响，而目前我们对其影响程度和生态机制却知之甚少。本研究针对水库特有水文情势与库尾溪流底栖动物群落耦合关系不明这一科学问题，以三峡水库库尾溪流白夹溪为研究区域，采用多维度、多学科、多层面的综合调查分析方法，研究库尾溪流底栖动物的群落结构、时空分布和生活史特征，阐明河库两相交替水位变动对库尾溪流底栖动物种类组成和群落结构的影响，揭示不同水位变动强度干扰下底栖动物时空动态过程及生态适应对策，分析底栖动物与水文、水质、河流生境等环境因子的关系，探索其中所涉及的生态调控机制。本研究是对尚未了解的库尾溪流底栖动物多样性、时空格局及环境响应机制的探索性认识，对于研究水库河流区水位变动影响下溪流生态格局和生态过程至关重要，同时也将为水库生态系统健康的维持及可持续管理提供科学依据。

受三峡水库蓄水影响的开县白夹溪水潭生境中共有大型底栖动物14种，属5目11科14属。优势种类主要是菱跗摇蚊Clinotanypus sp.、水丝蚓Limnodrilus sp.、摇蚊Camptochironomus sp.、细蜉Caenis sp.。从群落结构上看，摇蚊、颤蚓在大多数采样点的绝大多数采样季节中均为优势类群；蜉蝣在退水期成为部分样点的优势类群。靠近河口的样点底栖动物密度在蓄水期较高，在退水期偏低；距离河口较远的样点正好相反。各个采样点物种丰富度普遍较低。水淹时间较长的样点在退水期底栖动物多样性底，在蓄水期多样性较高；上游水淹时间较短样点与之相反。水质对各采样点底栖动物组成并无明显影响，但是水深、退水期流速、蓄水时间等水文因子对底栖动物群落影响较大。浅滩生境的底栖动物与水潭生境的底栖动物差异明显。前者以蜉蝣目昆虫为主，后者主要是摇蚊和颤蚓。浅滩的底栖动物的密度、多样性显著高于水潭。浅滩的底栖动物大致在退水后2个月后恢复到最高水平，但是其多样性水平依然低于未受到三峡水库蓄水淹没的自然浅滩。