HR: 08:30h
AN: PP51G-03    [Abstracts]
TI: Diagenesis, redistribution, and dilution of biomarkers in surface sediments of the Ross Sea
AU: * Hayes, J M
EM: jhayes@whoi.edu
AF: Dept. Geol. and Geophys., Woods Hole Oceanographic Institution, Woods Hole, MA 02543 United States
AU: Villiinski, J C
EM: villinjc@bp.com
AF: Biogeochem. Labs., Dept. Geol. Sci., Indiana Univ., Bloomington, IN 47405 United States
AU: Villiinski, J C
EM: villinjc@bp.com
AF: BP America, 501 Westlake Park Blvd., Houston, TX 77079 United States
AU: Brassell, S C
EM: simon@indiana.edu
AF: Biogeochem. Labs., Dept. Geol. Sci., Indiana Univ., Bloomington, IN 47405 United States
AU: Riggert, V L
EM: riggervl@bp.com
AF: BP America, 501 Westlake Park Blvd., Houston, TX 77079 United States
AB: Concentrations and carbon-isotopic compositions of sterols and of total organic carbon (TOC) have been measured at 18 stations in the Ross Sea. The samples were collected in December, 1997 and January, 1998 as part of the ROAVERRS program (Research on Ocean-Atmosphere Variability and Ecosystem Response in the Ross Sea). Numerous correlative observations of surficial and benthic conditions and processes are available from that program. Moreover, radiocarbon analyses are available for 39 sites within the study area. Independent of productivity, concentrations of TOC are highest at basin and slope sites and lowest on crests (sites with high measured bottom currents) and banks. Concentrations of sterols vary from 3 to 1120 (umol sterol C)/(mol TOC). Radiocarbon levels indicate that low concentrations of sterols are due mainly to dilution of autochthonous inputs by older materials. The effect is stronger at bank and crest sites and the diluent is mainly reworked sedimentary debris rather than recycling continental debris. Calculations comparing the decay of carbon-14 and the degradation of TOC and sterols indicate that the first-order rate constant for degradation of sterols exceeds that for TOC by 0.002 inverse years. Polytopic vector analysis resolves four end-member suites of sterols. The two most abundant account for 33 and 28 percent of all sterols and derive respectively from diatoms and from heterotrophs. The others (each 20 percent) derive from the Phaeocystis-dominated community associated with blooms in the Ross Sea Polynya and from a combination of dinoflagellates and microbial heterotrophs. The isotopic compositions of TOC and of algal sterols are weakly correlated (correlation coefficient = 0.51). Weighted-average delta values for algal sterols cover the range from -33.2 to -27.6 permil. In contrast, delta values for TOC cluster in two groups at -27 and -23 permil. The latter sites are concentrated at the western margin of the Ross Sea. This distribution duplicates that observed in particulate organic carbon in surface waters. At least for TOC, therefore, redistribution of organic carbon has not obscured the strongest isotopic feature in the Ross Sea.
DE: 4804 Benthic processes/benthos
DE: 4863 Sedimentation
DE: 4207 Arctic and Antarctic oceanography
DE: 3022 Marine sediments--processes and transport
DE: 1055 Organic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting