Response of diatom community in Lugu Lake (Yunnan–Guizhou Plateau, China) to climate change over the past century

Abstract

A mean annual temperature increase has been recorded on the Yunnan–Guizhou Plateau of China during the last century. This temperature increase has been significantly greater since the 1950s. Thus, paleolimnological analyses may be utilized to better understand ecological responses to recent changing climate over decadal to centennial timescales, especially in regions with sparse lake monitoring data. Here, we present paleolimnological results from a 210Pb/137Cs-dated sediment core spanning approximately the last ~250 years from a remote, alpine, semi-closed oligotrophic lake (Lugu Lake) on the northwestern Yunnan–Guizhou Plateau. Sediment profiles of diatoms, geochemical variables (LOI550, TOC and C/N) and median grain size were analyzed and compared with the climate data (1951 AD–2010 AD) from the Lijiang weather station. Endogenous productivity of Lugu Lake has increased gradually over the last 30 years. The majority of diatom taxa encountered in the core are typical of alkaline oligotrophic lakes. Diatom assemblages were dominated by Cyclostephanos dubius, Cyclotella taxa, and fragilarioid taxa. Diatom species composition has changed significantly with three assemblage shifts at different scales over the ~250-year period. Diatom species diversity reveals a distinct increase before ~1970 AD, followed by a decline. In addition, a decreasing trend in diatom cell-size was consistent with recent warming trends. Redundancy analysis (RDA) shows that regional air temperature trends (annual, spring, summer, and winter) have played a significant role (p < 0.05) in determining diatom compositional changes over the past six decades. Results of this study suggest that regional warming is the main driving force behind recent changes in diatom composition at Lugu Lake, while nutrients may also have impact on the diatom change in recent 10 years.