SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 5:00:00 PM
Location: Carson B
SunMY, University of Georgia, Athens, USA,
Ding, H, B, University of Georgia, Athens, USA, 
Degradation of Emiliania huxleyi-derived alkenones in stratified seawaters and at simulated oxic and anoxic sediment-water interfaces
We conducted a series of laboratory incubation experiments to examine degradation of Emiliania huxleyi-derived alkenones (37:2, 37:3, 38:2, and 38:3) in oxic and anoxic systems. One system consisted of oxic and anoxic seawaters, which were collected from stratified water column in Cariaco Basin. Another system was a simulated oxic and anoxic sediment-water interface, which was constructed by a thin (1 mm) layer of sediment and a large volume of seawater. Both sediment and seawater were taken from Georgia coast. Cultured Emiliania huxleyi cells were added to these systems for 2-3 month incubations. Our results showed: (1) all alkenones degraded faster (~ 2x) under oxic than anoxic conditions in both water and interface systems; (2) degradation rate constants measured in water system were higher (> 2x) than those measured in the interface system; (3) oxic degradation of alkenones in water and interface systems was complete in approximately one month; (4) there were generally two fractions of alkenones with different degradation rates under anoxic conditions in both systems; (5) there were some alkenones remained after 2-3 month anoxic incubations (~ 10% of initial concentration in water system and ~ 20% in the interface system); (6) there were no apparently preferential degradation of highly-unsaturated (37:3 and 38:3) relative to less-unsaturated (37:2 and 38:2) alkenones. These results implies that oxic degradation in water and at sediment-water interface may significantly reduce amount of alkenones but not alter application of alkenone ratio as paleotemperature indicator.