Reconstructing past continental climates is crucial for predicting future climate change, but reliable temperature proxies are scarce. This study demonstrates that heterocyte glycolipids (HGs) from diazotrophic cyanobacteria are widely distributed in freshwater environments. The relative abundance of HG26 diols and keto-ols, quantified by the heterocyte diol index (HDI26), strongly correlates with surface water temperature (SWT). Applying HDI26 to a 37,000-year Lake Tanganyika sediment record reveals a 4.1 °C warming from the last glacial maximum to the present. The widespread distribution of HGs suggests HDI26 can reconstruct SWT variations in various freshwater environments, improving our understanding of past continental climate change.

Thorsten Bauersachs, James M. Russell, Thomas W. Evans, Antje Schwalb, Lorenz Schwark