Bronk, D. A.. University of Georgia, dbronk@arches.uga.edu
Sanderson, M. A.. University of Georgia, mps@arches.uga.edu
Koopmans, D. J.. University of Georgia, dirk@arches.uga.edu

 
CHARACTERIZATION AND BIOAVAILABILITY OF DISSOLVED ORGANIC NITROGEN IN TWO GEORGIA RIVERS
 
In the waters of Georgia, up to 90% of the nitrogen entering the coastal zone is organic, derived primarily from marshes. One third of this organic material is humic substances, the biological availability of which is largely unknown. In this study, our objectives were, first, to characterize the DON pool using molecular weight fractionation and wet chemical analysis of urea, dissolved primary amines (DPA), proteins, and humics. Second, to use newly developed N15 tracer techniques to produce N15 labeled humic substances in the laboratory. Third, to determine the rate of uptake of humic nitrogen, and then compare this rate to uptake rates of inorganic nitrogen (ammonium, nitrate, and nitrite) and forms of organic nitrogen (urea, DPA, and protein) during 6 to 24 hr incubations. We measured rates of nitrogen uptake during spring, summer, and fall 1997 at four sites along the salinity gradient of the Savannah and Altamaha Rivers. Preliminary data suggest that 57 to 65% of the nitrogen at our sites was organic, and that humic nitrogen was bioavailable during short-term incubations. Based on these data, we suggest that humic substances can be a significant and previously unrecognized nitrogen substrate for the plankton community.
 
Day: Tuesday, Feb. 2
Time: 03:30 - 03:45pm
Location: Eldorado Hotel
 
Code: SS34TU0330E