Controlled lacustrine microcosms show a brGDGT response to environmental perturbations

Abstract

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) have proven useful for paleoclimate reconstructions. Nevertheless, the mechanism by which these biomarkers respond to the environment and the identity of the source organisms, remain poorly understood. These gaps in knowledge have prevented the study of brGDGTs in culture, thereby limiting the use of these molecules as a tool for paleoclimate reconstruction. In this work we used controlled microcosms to study the effect of temperature and pH on brGDGTs in lake water. Our results show that temperature has a strong influence on the production of brGDGTs, with a sensitivity that is similar to empirical observations. In contrast, the pH experiments yielded inconclusive results, either due to a limited response, or to the experimental set up. This study demonstrates that the brGDGT response to temperature can be replicated under controlled conditions, establishing that microcosms are a viable strategy to better understand the proxy response mechanism.