GCRC Program Summary |
Findings
Georgia Rivers Land Margin Ecosystem Research Program:
A comparative study of the transport and transformation of materials from rivers through the land-sea margin.
CDOM, FDOM, and DOM photochemistry:
DOM in the Georgia
estuaries and other terrestrially-influenced aquatic environments is characterized
by the abundance of light-absorbing or 'chromophoric' components. This CDOM
influences carbon biogeochemistry in the Georgia estuaries in many ways, for
example by acting as a source of biologically active photoproducts and by competing
with primary producers for solar radiation (Bushaw et al. 1996, Miller &
Moran 1997, Moran & Zepp 1997, Moran & Zepp 1999, Bushaw-Newton &
Moran 1999). Some fraction of the light absorbed by CDOM is re-emitted as fluorescence,
and thus fluorescent DOM (or FDOM) provides a sensitive measure of terrestrial
DOM concentration and source (Sheldon & Moran, in prep.). FDOM fluorescence
data paint a highly dynamic picture of the DOM pool in GARLMER rivers, and indicate
inputs from freshwater sources, intertidal marsh sources, and even marine sources
for some river estuaries, in contrast to bulk DOC measures that generally indicate
simple conservative mixing of freshwater DOM through the estuaries. The GARLMER
FDOM studies are currently being extended offshore through collaboration with
the ONR-funded South Atlantic Bight Synoptic Offshore Observation Network (SABSOON)
to provide real-time observational data on terrestrially-derived FDOM on the
U.S. southeastern continental shelf. Through the SABSOON project, CDOM fluorometers
are being mounted on an offshore tower grid and will provide continuous surface
and bottom monitoring of CDOM concentrations, along with a suite of other meteorological
and oceanographic variables. CDOM data from riverine and coastal endmembers
obtained as part of our GARLMER research will help establish the first data
set on the magnitude and variability of terrestrial inputs to the land/ocean
margin of the southeastern U.S.