Do changes in water depth and water level influence the diatom diversity of Yunlong Lake, in Yunnan Province, Southwest China?

Exploring whether diatom diversity in a lake sediment core is representative of that of the entire lake is important for determining the response of lake diatom diversity to global climatic warming. In this study, Yunlong Lake, an alpine lake located in Yunnan Province, Southwest China, was investigated to explore this question over both space and time. Spatially, we investigated diatom diversity patterns in 62 surface sediment samples from different locations and depth zones of Yunlong lake and found essentially constant diatom diversity across the entire lake basin. Temporally, we studied a well-dated sediment core from the lake center to explore whether long-term water-level changes influenced diatom diversity over the last ~ 100 years. Changes in the annual average sediment accumulation rates indicate that the water level of Yunlong Lake increased substantially after the construction of a dam. However, there is no obvious relationship between diatom diversity and water-level changes, which suggests at this site long-term water-level changes did not influence diatom diversity. Comparative analysis of the results for Yunlong Lake with those for other lakes indicates that for relatively strongly mixed lakes with a simple morphology and uniform shoreline microhabitat, such as Yunlong Lake, differences in water depth and changes in water level may not influence diatom diversity. In such cases, the diatom diversity from a sediment core is likely to be representative of that of the entire lake during specific time intervals. Therefore, such lakes may be optimal for studies of changes in past diatom diversity using sediment cores.