First Pediastrum–temperature transfer function and its application to mid-to-late Holocene reconstruction in Central Asia

The green alga Pediastrum is an ecologically significant component of freshwater ecosystems, but its potential as an independent proxy for quantitative paleoenvironmental reconstruction is relatively unexplored. Here we use multivariate statistical analysis to explore the relationship between the Pediastrum composition of lake surface sediments and environmental variables. The findings highlight the mean growing season air temperature between March and October (TMar-Oct) as the most important factor determining the Pediastrum composition. We then establish the first transfer function between the Pediastrum taxa and TMar-Oct, which enables us to provide a quantitative temperature reconstruction for the past ∼8.2 kyr based on sedimentary subfossil Pediastrum records from Bosten Lake in Xinjiang, China. Our findings reveal an exceptionally warm climate during ∼4.8–3.6 kyr, with temperatures ∼4 °C higher compared to those during ∼8.2–4.8 kyr. This unusually warm climate is verified by the carbonate clumped isotopes record of the same core and other paleoclimate records. These findings contribute to our understanding of past temperature changes in Central Asia and provide a basis for future research on long-term lake ecosystem dynamics under past climatic warming.