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Abstract
Chromophoric dissolved organic matter (CDOM) variability in Barataria Basin, Louisiana,
USA,was examined by excitation emission matrix (EEM) fluorescence combined with parallel
factor analysis (PARAFAC). CDOM optical properties of absorption and fluorescence
at 355nm along an axial transect (36 stations) during March, April, and May 2008 showed
an increasing trend from the marine end member to the upper basin with mean CDOM absorption
of 11.06 + or - 5.01, 10.05 + or - 4.23, 11.67 + or - 6.03 (m(-)(1)) and fluorescence
0.80 + or - 0.37, 0.78 + or - 0.39, 0.75 + or - 0.51 (RU), respectively. PARAFAC analysis
identified two terrestrial humic-like (component 1 and 2), one non-humic like (component
3), and one soil derived humic acid like (component 4) components. The spatial variation
of the components showed an increasing trend from station 1 (near the mouth of basin)
to station 36 (end member of bay; upper basin). Deviations from this increasing trend
were observed at a bayou channel with very high chlorophyll-a concentrations especially
for component 3 in May 2008 that suggested autochthonous production of CDOM. The variability
of components with salinity indicated conservative mixing along the middle part of
the transect. Component 1 and 4 were found to be relatively constant, while components
2 and 3 revealed an inverse relationship for the sampling period. Total organic carbon
showed increasing trend for each of the components. An increase in humification and
a decrease in fluorescence indices along the transect indicated an increase in terrestrial
derived organic matter and reduced microbial activity from lower to upper basin. The
use of these indices along with PARAFAC results improved dissolved organic matter
characterization in the Barataria Basin.