Biomarker and Isotope Studies of Organic Matter Cycling in the Black Sea: A Focus on Bacteria and Archaea

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ABSTRACTOCE-0117824The study, a collaboration between Skidaway researchers and a group at Texel (NIOZ -Netherlands) will carry out molecular biomarker studies of particulate organic matter (POM) and surface sediments of the Black Sea in order to delineate the distributions of archaeal and bacterial biomarkers, and putatively their source microorganisms. The Black Sea environment is chosen to provide a strongly stratified, yet readily sampled, bioreactor system that is characteristic of anoxic marine basins, past and present. Anaerobic methane oxidation, a globally important but poorly understood process in such systems is of considerable interest, given recent suggestions that archael species may be much more common in oxic and euphotic oceanic environments than previously thought. Membrane lipids, derived from the isoprenoid skeletons of di- and tetraethers, are a diverse group of compounds whose presence provides a useful diagnostic for the presence of thermophilic, psychrophilic and other groups amongst the Archaea. The identification of which archael groups inhabit what microhabitat (oxic, anoxic, hypoxic etc) zones within the water column and underlying sediments is likely to be an important key to the interpretation of other synoptic assessments of their microbial ecology, community structure and function. Lipid measurements, readily made by modern GC, GC-MS and LC-MS techniques, may enhance and extend proposed detailed and exacting genomic probing of these complex microbial systems.Additional insight into carbon cycling and preservation in the Black Sea system will be gained from investigation of the 13C stable isotopic composition of these molecular biological indicators. Such measurements are increasingly made possible by compound specific isotopic analysis (csia) methods. Broader impacts into the study of organic matter cycling in the Black Sea relate to continued definition of the impact of archaeal prokaryotes on the earth's biogeochemical cycles, their role in consuming sedimentary and water column CH4 (which may otherwise be a very important greenhouse gas), use of their lipid biomarkers in reconstructing past climate change, and clues to further specification of their exotic cellular and enzymic biochemistries.