Novel biomarker application reveals the microbial ecological dynamics surrounding Oceanic Anoxic Event II (OAE-2)

Abstract

Biomarkers are established facets of paleoenvironmental study, yet significant untapped potential remains. Conventional methods (e.g. GC-MS) fail to characterize large, polar molecules, which often possess greater biological specificity than saturated or aromatized hydrocarbons, while approaches leveraging the expanded analytical window intrinsic to LC-MS are frequently focused on a single compound class. Here, application of a novel LC-qTOF-MS method enabled simultaneous monitoring of numerous biomarkers, leading to the concept of a biomarker inventory populated with biosynthetic derivatives of marine microbial communities spanning the epipelagic to benthic realms. This comprehensive approach granted unparalleled insight into microbial ecological dynamics surrounding OAE-2, addressing outstanding enigmas related to the spatiotemporal evolution of organic carbon burial drivers. An extensive reassessment of previously discounted biomarkers revealed significant paleoreconstructive potential by tracking pelagic redox fluctuations in a menagerie of depositional settings, especially useful for delineating periods of marine deoxygenation (i.e. OAEs) in the geologic record. Critical evaluation of a potential OAE-2 trigger revealed both transient and enduring biochemical shifts relevant to an apparent association with enhanced organic carbon burial. However, the relationship between cause (i.e. trigger) and effect (OAE-2) was substantiated by currently unconsidered mechanisms that fundamentally alter the invocation of this trigger in paleoenvironmental research. This dissertation, documenting the incipient findings of method application, highlights the immense potential of LC-qTOF-MS as a cipher to decode the molecular signatures bound in the sedimentary archives.