Department of Ecology, Jinan University, Guangzhou 510632, China.
Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China.
Water Res. 2017 Nov 1;124:618-629. doi: 10.1016/j.watres.2017.07.078. Epub 2017 Aug 1.
Warming has pronounced effects on lake ecosystems, either directly by increased temperatures or indirectly by a change in salinity. We investigated the current status of zooplankton communities and trophic structure in 45 Tibetan lakes along a 2300 m altitude and a 76 g/l salinity gradient. Freshwater to hyposaline lakes mainly had three trophic levels: phytoplankton, small zooplankton and fish/Gammarus, while mesosaline to hypersaline lakes only had two: phytoplankton and large zooplankton. Zooplankton species richness declined significantly with salinity, but did not relate with temperature. Furthermore, the decline in species richness with salinity in lakes with two trophic levels was much less abrupt than in lakes with three trophic levels. The structural variation of the zooplankton community depended on the length of the food chain, and was significantly explained by salinity as the critical environmental variable. The zooplankton community shifted from dominance of copepods and small cladoceran species in the lakes with low salinity and three trophic levels to large saline filter-feeding phyllopod species in those lakes with high salinity and two trophic levels. The zooplankton to phytoplankton biomass ratio was positively related with temperature in two-trophic-level systems and vice versa in three-trophic-level systems. As the Tibetan Plateau is warming about three times faster than the global average, our results imply that warming could have a considerable impact on the structure and function of Tibetan lake ecosystems, either via indirect effects of salinization/desalinization on species richness, composition and trophic structure or through direct effects of water temperature on trophic interactions.
变暖对湖泊生态系统有明显的影响，无论是通过温度升高直接影响，还是通过盐度变化间接影响。我们调查了沿 2300 米海拔和 76 克/升盐度梯度的 45 个西藏湖泊中的浮游动物群落和营养结构的现状。从淡水到低盐湖泊主要有三个营养层次：浮游植物、小型浮游动物和鱼类/沼虾，而从中盐到高盐湖泊只有两个：浮游植物和大型浮游动物。浮游动物物种丰富度随盐度显著下降，但与温度无关。此外，在具有两个营养层次的湖泊中，物种丰富度随盐度的下降比在具有三个营养层次的湖泊中要平缓得多。浮游动物群落的结构变化取决于食物链的长度，并且受到盐度作为关键环境变量的显著解释。浮游动物群落从低盐和三个营养层次的湖泊中以桡足类和小型枝角类为主导，转变为高盐和两个营养层次的湖泊中以大型盐水滤食性磷虾类为主导。浮游动物与浮游植物生物量的比值与温度呈正相关，在两个营养层次的系统中是这样，而在三个营养层次的系统中则相反。由于青藏高原的变暖速度是全球平均水平的三倍多，我们的结果表明，变暖可能会通过盐度变化/淡化对物种丰富度、组成和营养结构的间接影响，或通过水温对营养相互作用的直接影响，对西藏湖泊生态系统的结构和功能产生重大影响。
