Innovating Sediment Oxygen Consumption Quantification: A Novel Proxy Utilizing Marine Bacterial Tetraether Lipids

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"Marine sediments serve as Earth's primary repository for organic matter, playing a pivotal role in the global carbon and oxygen cycles. Sediment oxygen consumption (SOC) is a key metric for assessing the degradation and preservation of sedimentary organic matter and for gauging the activity levels of benthic communities. However, current methods for measuring SOC face limitations, notably their reliance on specialized, costly instrumentation and their lack of applicability in geological contexts. Here, we propose a novel, lipid-based approach for quantifying SOC using branched glycerol dialkyl glycerol tetraethers (brGDGTs). These bacterial membrane lipids have been extensively used in paleoclimate reconstructions. Recent advances highlight the widespread production of brGDGTs by benthic marine bacteria and the significant role of oxygen in brGDGT production and distribution. Our preliminary data indicate strong correlations between brGDGTs and SOC, hinting at a potential tool for assessing SOC in both modern and paleo marine sediments. To thoroughly address the scientific question, ""How can brGDGTs be used to assess modern and paleo SOC?"" this proposal sets forth to: 1) establish a robust, quantitative proxy for SOC by rigorously investigating the linkage between brGDGTs and SOC, utilizing multidisciplinary methodologies encompassing biomarker lipids, oxygen microprofiles, microbial communities, and geochemical analyses in geographically diverse sediments; 2) evaluate the proxy’s effectiveness and limitations through laboratory incubations; and 3) assess the proxy’s applicability for paleo SOC reconstructions. This research will broaden our knowledge of the ecophysiological behaviours of marine brGDGT-producing bacteria, enhance the precision of brGDGT applications in paleoclimate reconstructions, and pioneer an innovative molecular proxy for SOC quantification across diverse spatiotemporal scales."