HR: 1340h
AN: OS33A-0577    [Abstracts]
TI: Major Sterol Fluxes in Sinking Particles and Surface Sediments in the Cariaco Basin.
AU: * Woodworth, M P
EM: mwoodworth@geol.sc.edu
AF: University of South Carolina , Department of Geological Sciences; , Columbia, SC 29208 United States
AU: Goni, M A
EM: goni@geol.sc.edu
AF: University of South Carolina , Department of Geological Sciences; , Columbia, SC 29208 United States
AU: Thunell, R
EM: thunell@geol.sc.edu
AF: University of South Carolina , Department of Geological Sciences; , Columbia, SC 29208 United States
AU: Tappa, E
EM: ejt@geol.sc.edu
AF: University of South Carolina , Department of Geological Sciences; , Columbia, SC 29208 United States
AU: Astor, Y
EM: yastor@edimar.org
AF: Fundacion La Salle de Ciencias Naturales, Estacion de Investigaciones Marinas de Margarita, Porlomar, 6301 Venezuela
AB: Sterols in sediments are used to trace past ecosystem dynamics in the upper ocean. It is therefore important to know what factors control the creation of sterol fluxes, degradation of sterols in the water column and eventual burial in the sediments. To this end we examined the major sterols fluxes in sediment traps during 1996-1997 (at depths of 275, 455 and 975m) and surface sediments in the Cariaco Basin. Sterol flux data in the sediment traps were compared with hydrographic data collected as part of the CARIACO Project. Diatom sterols 24-methylcholesta-5,22-dien-3b-ol (brassicasterol), 24-methylcholesta-5,24(28)-dien-3b-ol (24methlyene-cholesterol) fluxes were greatest during upwelling. 24methlyene-cholesterol was well correlated with biogenic opal flux (r$^{2}$ = 0.88) suggesting that 24methlyene-cholesterol is an excellent biomarker for diatom production. 4a,23,24-trimethyl-5a(H)-cholest-22-en-3b-ol (dinosterol) exhibited a post upwelling maximum indicating that fluxes of dinoflagellate-derived materials were dominant during stratified conditions. Sterols were degraded with depth but the relative composition of the major sterols remained fairly constant. There is a sharp decrease in the magnitude of total sterol fluxes between the sediment traps (955m; 143 ug m$^{-2}$ d$^{-1}$) and the surface sediments (core depth 460m; 11.7 ug m$^{-2}$ $^{-1}$) indicating that a large portion of the flux is lost at the sediment water interface. It is at this transition in which the relative compositions of the sterols are also altered. Dinosterol, which is a minor component of the sediment trap fluxes, is 3 to 4 times greater than that of cholesterol in the sediment. While the ratio of dinosterol to cholesterol changed significantly, the ratio between the two diatom sterol fluxes, brassicasterol and 24methlyene-cholesterol, and cholesterol remained within the range of values observed in the sediment traps.
DE: 4808 Chemical tracers
DE: 4850 Organic marine chemistry
DE: 4800 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL
DE: 4802 Anoxic environments
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting