HR: 08:15h
AN: PP51D-02 INVITED    [Abstracts]
TI: Marine Archaea lipids: patterns and provenance in the water-column
AU: * Turich, C
EM: courtney.turich@skio.usg.edu
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802, United States
AU: * Turich, C
EM: courtney.turich@skio.usg.edu
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, United States
AU: Freeman, K H
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802, United States
AU: Bruns, M
AF: Pennsylvania State University, Department of Crop and Soil Sciences, University Park, PA 16802, United States
AU: Conte, M
AF: Bermuda Institute for Ocean Sciences, Ferry Reach, St. Georges, GE01, Bermuda
AU: Jones, A
AF: Michigan State University, Department of Biochemistry and Molecular Biology, East Lansing, MI 48824-1319, United States
AU: Wakeham, S G
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, United States
AB: The paleotemperature proxy TEX86 (TetraEther indeX) is based on a robust correlation between the ratio of marine archaeal lipids (glycerol dialkyl glycerol tetraethers (GDGTs) with different numbers of rings), and temperature. The potential paleoceanographic utility of this proxy is tremendous, and it has already been used successfully in a number of paleoenvironments (e.g. Younger Dryas detection in the southern hemisphere) but poses problems in others (e.g. the southern North Sea with high sediment input). The physiological, phylogenetic, and physical controls on this correlation remain speculative and difficult to test. Different archaeal subgroups live throughout the water column (some with unknown metabolisms), only one representative of marine Crenarchaeota and no marine Euryarchaeota are available in pure culture for experimentation, and lipid ratios observed in enrichment versus in situ samples inexplicably differ. We hypothesize that lipid distribution patterns are affected by ecological changes. We measured archaeal lipids from globally distributed samples of freshwater, marine, and hypersaline suspended particulate matter. Cluster analysis of relative lipid distributions identified four distinct groups, including: 1) marine epipelagic waters, 2) marine mesopelagic/upwelling waters, 3) freshwater/estuarine waters, and 4) hypersaline waters. We propose that community changes regulate the lipid patterns distinguishing these groups, including epipelagic and mesopelagic/upwelling zones. Lipid patterns in mesopelagic/upwelling waters are similar to those expected for nitrifying Group I Crenarchaeota-- predominance of crenarchaeol and abundant cyclic GDGTs. Non-metric multidimensional analysis shows this pattern is associated with high nitrate concentrations. Furthermore, the difference between calculated TEX86 temperature and in situ temperature from surface to deep waters correlates with nitrate concentrations, enforcing a connection between community change (esp. increase/dominance of nitrifying Crenarchaeota) and TEX86 values. The combination of cluster analysis and ordination of lipid patterns, contextualized with environmental factors suggest observed values of TEX86 are subject to changes in archaeal ecology, possibly influenced by nutrient fluctuations or other perturbations can affect both surface and deeper water GDGT production, preservation, and transport. In paleoceanographic applications, TEX86 lipids may not record only temperature, but equally interesting changes in nutrient concentrations, oceanographic conditions, and ecology.
DE: 1055 Organic and biogenic geochemistry
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting