Microbial Community Drives BrGDGT Response to Environmental Changes in Freshwater Microcosms
Abstract
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) have proven useful for paleoclimate reconstructions. Nevertheless the mechanism by which these biomarkers respond to environmental factors and the identity of the source organisms still remain poorly understood. These gaps in knowledge have prevented the study of brGDGTs in culture, thereby limiting our understanding of these molecules as a tool for paleoclimate reconstruction.
In this work we combine lipid analysis and 16S rRNA amplicon sequencing to study the effect of environmental perturbations (temperature, pH, and glucose) on both brGDGTs and the microbial communities of lake water under laboratory conditions. Our results show that temperature has a strong influence on the production, methylation, and isomerization of brGDGTs and that this response appears to be linked to three distinct groups of microorganisms, associated with specific brGDGT molecules. In our samples, these groups are predominantly composed of members of the Proteobacteria phylum, with Acidobacteria showing no significant relationship. Furthermore, in our experiments we observe little response of brGDGTs to other environmental factors, such as pH and carbon source. Our results are in line with previous work suggesting that brGDGT response to environmental perturbation is driven by changes in the microbial population rather than a metabolic response (1). Furthermore, their observed sensitivity to temperature in our incubations is remarkably close to the empirical calibration for African lakes (2). This is a promising result that supports the general use of this biomarker proxy. 1. De Jonge, Cindy, et al., Organic Geochemistry , 2019. 2. Russell, James M., et al., Organic geochemistry , 2018, vol. 117, p. 56-69.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B51C..02M
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES;
- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY;
- 4924 Geochemical tracers;
- PALEOCEANOGRAPHY