Exploration of Fossil DNA-Based Geobiologic Archives to Reconstruct Hydrologic Changes in the Black Sea during the Holocene

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Abstract (Coolen OCE-0602423)To date, DNA-based sedimentary archives in marine systems have remained largely unexplored. This project represents the first detailed application of ancient DNA to a large marine basin in order to develop records of past water column structure. The PIs propose to develop parallel, high temporal resolution (50-100 yr) DNA and lipid biomarker based stratigraphic records of water column and microbial community structure in the Black Sea spanning the past 12,000 years of the Holocene when the system underwent dramatic climate-forced physical and chemical changes. Targeted molecules will include markers for microbial communities dwelling at the surface (algal primary producers), the suboxic layer (marine Crenarchaeota), and the sulfidic chemocline (obligate anoxyphotolithotrophic GSB) in order to provide information on past surface water temperature, salinity and stratification change in the Black Sea. Side-by-side phylogenetic and lipid biomarker analyses will be performed in order to carefully assess the validity of utilizing ribosomal DNA and functional genes as proxies of a given biological input and to assess the influence of species changes in the putative biological precursors on both the distribution and isotopic composition of corresponding lipid biomarkers. Primary objectives of this project include (1) An examination of the breadth and fidelity of paleoenvironmental information encoded in DNA sedimentary archives, (2) Application of DNA studies to further our understanding of the utility and limitations of lipid biomarker proxy records and (3) Application of combined DNA and lipid molecular stratigraphic tools to refine interpretations of climate-driven hydrologic changes in the Black Sea during the Holocene. This project will form the centerpiece of a PhD dissertation of a WHOI/MIT Joint Program student. The recognition that DNA can be preserved in aquatic sediments over many millennia represents an important step forward in our ability to examine the relationships between climate and biological diversity.