化石摇蚊与水深之关系：一种西北干旱区水文气候变化重建工具

significant relationship between the distribution and abundance of chironomids and water depth has long been recognized. However, few studies have been carried out on this topic in arid regions where the chironomid community is usually controlled by water salinity. Thus Bosten Lake, the largest inland freshwater lake (approx. 1200 km2) in China and located in the northwest of the country, provides a unique opportunity to investigate this relationship in an arid region. A total of 42 surface sediment samples, from water depths of 0 m to 17 m, and 12 chironomid taxa were used in the analysis. The first PCA axis explained 59.3% of the variance in the chironomid assemblage and there was a significant correlation between PCA axis 1 scores and water depth (r2 = 0.84, P < 0.001). The chironomid assemblages significantly changed at 8.0 m. This threshold corresponded to an abrupt change in the underwater slopes and the spatial pattern of aquatic vascular plants. RDA showed that the abundance of Chironomus plumosus-type, Microchironomus and Cryptochironomus was positively correlated with water depth, whereas the abundance of Tanytarsus, Polypedilum nubifer-type, Cricotopus and Psectrocladius sordidellus-type was negatively correlated with water depth. These ecological relationships have been supported by the literature. The qualitative chironomid-inferred changes in lake level and qualitative diatom-inferred changes in salinity from a sediment core BSTC001 were also compared. The close agreement in trends of these two variables validates the use of chironomid assemblages to study palaeo-hydrological variability in this westerly-dominated arid region.