Laboratory and Field Studies on the Cycling of Archae- bacterial Lipids in the Orca Basin, an Anoxic Hypersaline Basin in the Gulf of Mexico

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In marine systems where high salinity, high temperature, low pH, or extreme anoxicity characterize the environment, archaebacteria (including methanogens, extreme halophiles, and thermoacidophiles) play a dominant role in the cycling of organic carbon. Isopranyl glycerol ethers have recently been recognized as a characteristic morphological feature in identifying and differentiating archaebacteria. In order to use these compounds as geomolecular markers, it is first necessary to understand their cycling in the environment. Dr. Van Vleet proposes to investigate potential diagenetic alteration products of these compounds using a series of laboratory thermal alteration experiments and to use these diagnostic organic molecules to investigate their distribution and cycling in the Orca Basin, a well studied anoxic hypersaline basin in the Gulf of Mexico. %%% Objectives of the proposed study are (1) to investigate the alteration of isopranyl ether-linked lipids in the environment by using laboratory heating experiments combined with analysis of kerogen cleavage products to simulate diagenetic processes, (2) to examine the distribution of archaebaterial ether-linked lipids in the Orca Basin, including the overlying water, halocline, brine, surface sediments and selected DSDP sediments, and (3) to combine information on the distribution of archaebacterial ether lipids in the Orca Basin with data obtained from laboratory thermal alteration studies to eluciate the diagenetic pathways of archaebacterial ether lipds in the environment. Results of this study will provide a basis for investigating microbial ecology in the Orca Basin and may also serve as a model for other marine anoxic or hypersaline systems.