McCarthy, M. D. Ecole Nationale Superior de Chimie,
Hedges, J. D. University of Washington, jihedges@ocean.washington.edu
Benner, R. University of Texas, benner@utmsi.ut.edu
Fogel, M. Carnegie Institute of Washington, fogel@gl.ciw.edu

 
MOLECULAR-LEVEL STABLE CARBON AND NITROGEN ISOTOPIC COMPOSITION OF AMINO ACIDS IN OCEANIC DISSOLVED ORGANIC MATTER
 
Most dissolved organic nitrogen (DON) in the open sea resides in amide structures that can not be readily identified at the molecular level. Amino acid compositions and enantiomeric ratios indicate a large component of this nitrogenous material is derived directly from bacterial cell wall structural polymers. However, molecular-level amino acid compositions provide little information on sources of the major proteinaceous component, much of which is likely difficult to recover with traditional hydrolysis methods. Stable isotopic compositions of individual amino acids, however, show large and characteristic fractionations which may have the potential to discriminate proteinaceous sources from different groups of organisms. We present here the first stable carbon as well as nitrogen isotopic compositions of individual amino acids from oceanic dissolved organic matter. Analogous measurements were also made on several cosmopolitan oceanic algal and bacterial species. These comparisons indicate that relative stable isotopic fractionation patterns of several specific amino acids- in particular Ala and Gly- represent strong potential tracers for oceanic proteinaceous sources. Based on these patterns, the amino acid isotopic signatures from natural dissolved organic matter from surface and deep water at three oligotrophic sites suggest an important bacterial origin for dissolved proteinaceous material at all depths in the open sea.
 
Day: Tuesday, Feb. 2
Time: 04:00 - 04:15pm
Location: Eldorado Hotel
 
Code: SS34TU0400E