Fluctuating lake levels are an important driver of ecosystem change, and changes in the precipitation/evaporation balance of a region can lead to undesirable changes in ecosystem functioning. Large-scale changes in hydrology will become increasingly more likely as a result of ongoing climate change in the coming century. This is especially true for the Tibetan Plateau, which plays a crucial role as the “Asian water tower” for the surrounding densely populated regions. Chironomids (Diptera: Chironomidae) have proven to be one of the most valuable bioindicators for monitoring and reconstructing the development of aquatic ecosystems. Besides temperature, water depth and salinity are two of the most important environmental factors affecting chironomids. To study the relationship between chironomids and water depth, we analyzed surface sediment samples of two large Tibetan lakes, Selin Co and Taro Co. These lakes have similar environmental conditions (e.g. elevation, temperature and oxygenation) but show strong differences in salinity (7–10 and 0.5 ppt, respectively). Our results show that the chironomid assemblages in both lakes have similar water depths at which the fauna abruptly changes in composition, despite different faunal assemblages. The most important boundaries were identified at 0.8 and 16 m water depth. While the uppermost meter, the “splash zone”, is characterized by distinctly different conditions, resulting from waves and changing water levels, the cause of the lower zone boundary remains enigmatic. Even though none of the measured water depth-related factors, such as water temperature, oxygen content, sediment properties, light intensity or macrophyte vegetation, show a distinct change at 16 m water depth, comparison to other records show that a similar change in the chironomid fauna occurs at 16 m water depth in large, deep lakes around the world. We propose that this boundary might be connected to water pressure influencing the living conditions of the larvae or the absolute distance to the surface that has to be covered for the chironomid larvae to hatch. We conclude that water depth either directly or indirectly exerts a strong control on the chironomid assemblages even under different salinities, resulting in distribution patterns that can be used to reconstruct past fluctuations in water depths.

湖泊水位波动是生态系统变化的重要驱动力，一个地区降水/蒸发平衡的变化可能导致生态系统功能发生不良变化。由于下个世纪持续的气候变化，大规模水文变化的可能性将越来越大。对于青藏高原尤其如此，青藏高原在周围人口稠密的地区扮演着“亚洲水塔”的角色。Chironomids（Diptera：Chironomidae）已被证明是监测和重建水生生态系统发展的最有价值的生物指标之一。除温度外，水深和盐度是影响猫科动物的两个最重要的环境因素。为了研究日光浴与水深之间的关系，我们分析了两个大型藏族湖泊Selin Co和Taro Co的地表沉积物样本。这些湖泊具有相似的环境条件（例如海拔，温度和氧合作用），但盐度差异很大（分别为7-10和0.5 ppt）。我们的结果表明，尽管不同的动物群落组合，两个湖泊中的手足类动物组合具有相似的水深，在该深度处动物群的成分会突然变化。在水深0.8和16 m处确定了最重要的边界。虽然最上面的仪表“飞溅区”的特征是波浪和不断变化的水位导致明显不同的状况，但较低区边界的原因仍然是个谜。即使没有测量到的与水深有关的因素，例如水温，氧气含量，沉积物特性，光照强度或大型植物植被在水深16 m处显示出明显的变化，与其他记录的比较表明，在世界上较大的深水湖泊中，在水深16 m时，尺虫动物群也发生了类似的变化。我们建议该边界可能与影响幼虫的生存条件的水压或与拟幼体孵化所必须覆盖的表面的绝对距离有关。我们得出的结论是，即使在不同的盐度下，水深也可以直接或间接地对手轮虫群施加强大的控制力，从而产生可用于重构过去水深波动的分布模式。与其他记录的比较表明，在世界深处的大型湖泊中，水深16 m时，尺虫类动物群发生了类似的变化。我们建议该边界可能与影响幼虫的生存条件的水压或与拟幼体孵化所必须覆盖的表面的绝对距离有关。我们得出的结论是，即使在不同的盐度下，水深也可以直接或间接地对手轮虫群施加强大的控制力，从而产生可用于重构过去水深波动的分布模式。与其他记录的比较表明，在世界深处的大型湖泊中，水深16 m时，尺虫类动物群发生了类似的变化。我们建议该边界可能与影响幼虫的生存条件的水压或与拟幼体孵化所必须覆盖的表面的绝对距离有关。我们得出的结论是，即使在不同的盐度下，水深也可以直接或间接地对手轮虫群施加强大的控制力，从而产生可用于重构过去水深波动的分布模式。我们建议该边界可能与影响幼虫的生活条件的水压或与拟幼体孵化所必须覆盖的表面的绝对距离有关。我们得出的结论是，即使在不同的盐度下，水深也可以直接或间接地对手轮虫群施加强大的控制力，从而产生可用于重构过去水深波动的分布模式。我们建议该边界可能与影响幼虫的生存条件的水压或与拟幼体孵化所必须覆盖的表面的绝对距离有关。我们得出的结论是，即使在不同的盐度下，水深也可以直接或间接地对手轮虫群施加强大的控制力，从而产生可用于重构过去水深波动的分布模式。