Teece, M. A. Carnegie Institution of Washington, teece@gl.ciw.edu
Fogel, M. A. Carnegie Institution of Washington, fogel@gl.ciw.edu
Benner, R. University of Texas at Austin, benner@utmsi.zo.utexas.edu

 
STABLE CARBON ISOTOPE COMPOSITION OF INDIVIDUAL CARBOHYDRATES IN OCEANIC DISSOLVED ORGANIC MATTER: ELUCIDATION OF POTENTIAL SOURCES.
 
The carbon isotope composition (d13C) of oceanic dissolved organic matter (DOM) is relatively constant (ca.-21.7 per mil), thereby suggesting a common marine source. The molecular composition of dissolved carbohydrates is also relatively constant regardless of depth or location and is distinctive from other marine materials, such as fresh plankton and sinking particles. The stable carbon isotope (d13C) compositions of individual neutral sugars of oceanic DOM from various depths in the equatorial Pacific and the Gulf of Mexico were similar. In all samples analyzed, the d13C of galactose was similar to the bulk material, whereas glucose was heavily enriched, by up to 12 per mil. DOM from the isotopically-depleted Mississippi and Rio Negro rivers displayed a similar signal of enriched glucose and the d13C of other neutral sugars shifted accordingly. The neutral sugars, therefore, may form by similar processes in both freshwater and oceanic systems. The distributions and isotope compositions of individual neutral sugars produced by possible sources of DOM, including bacteria, algae, zooplankton and plants, were measured. The distribution and isotope composition of algal carbohydrates differed significantly from that of DOM. Therefore, carbohydrates present in DOM directly produced by algae are unlikely to be a substantial source of recalcitrant UDOM. Conversely, secondary producers contained isotopically-enriched glucose, and therefore either heterotrophic bacteria or grazers are likely sources of DOM.
 
Day: Tuesday, Feb. 2
Time: 11:30 - 11:45am
Location: Eldorado Hotel
 
Code: CS56TU1130E