Developing molecular tools to estimate the biological sources of long chain diols : “Towards the improvement of a paleotemperature reconstruction proxy based on long chain diols”

Abstract

In recent years, multiple climate reconstruction proxies based on organic molecules have been developed. These proxies are proven to be of great importance to reconstruct past environmental conditions such as temperature. The Long chain Diol Index (LDI) is a novel paleotemperature proxy, which is based on Long-Chain Diols (LCD). These lipids are detected in marine and lacustrine environments and have been identified in several algal cultures, predominantly belonging to the Eustigmatophyceae, a Stramenopiles phylum. However, the biological source of the LCDs in the environment remains uncertain. In this study, we focused on eustigmatophytes as a possible source of LCDs and surveyed two different environments, with multiple stations around Iceland and Lake Challa, a stratified lake in Eastern Africa. With Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) in combination with designed primers we were able to quantify the 18S rRNA gene sequences of eustigmatophytes in suspended particulate matter (SPM). These results were compared to the abundance and composition of LCDs in the SPM and also with the LCDs that were obtained from sedimenting particles and surface sediment. We found a similar trend of the LCDs and the eustigmatophyte 18S rRNA gene sequence abundances in the water column. We also detected seasonal distributional changes of LCDs that might indicate different blooms of LCD producers and/or environmental conditions. Also, unique 18S rRNA gene sequences were amplified, which can indicate novel genera, belonging to the Eustigmatophyceae phylum.