McClelland, J. W. University of East Anglia, J.Mcclelland@uea.ac.uk
Holmes, R. W. The Ecosystems Center, rholmes@lupine.mbl.edu
Kroger, K. Boston University Marine Program, kroger@bio.bu.edu
Valiela, I. Boston University Marine Program, valiela@bio.bu.edu

 
NATURAL ABUNDANCE 15N OF NITRATE, AMMONIUM, DON, AND PON AS INTEGRATIVE MEASURES OF ECOSYSTEM PROCESSES: A CASE STUDY OF THE CHILDS RIVER ESTUARY, CAPE COD, MA
 
Improved methods for isolating different nitrogen pools from aquatic environments, combined with greater sensitivity of isotope ratio mass spectrometry, are making the use of multiple-pool 15N measurements an increasingly powerful approach for identifying ecosystem processes. Measurements from the Childs River estuary, Cape Cod, MA, exemplify this approach. Patterns of natural abundance 15N of watercolumn nitrate, ammonium, DON, and PON along the estuarine gradient of the Childs River were examined in winter and late spring. Stark differences in 15N patterns of DIN between sampling dates identify shifts in the dominant nitrogen transformations at work in the Childs River estuary between seasons. In particular, the roles of nitrification, denitrification, and uptake of nutrients by primary producers are considered. Differences in 15N patterns of DON and PON between sampling dates identify shifts in the contributions of terrestrial versus estuarine and marine sources between seasons. Comparisons of PON to inorganic N isotope values identify the dominant nutrient sources used by producers along the estuarine gradient. Simultaneous consideration of 15N in four major nitrogen pools has promoted an integrated understanding of N processing within the Childs River estuary. Such an approach would likely be beneficial for understanding nitrogen processing in other systems as well.
 
Day: Tuesday, Feb. 2
Time: 09:30 - 09:45am
Location: Eldorado Hotel
 
Code: SS32TU0930E