Engelhaupt, E. Tulane University, eengelh@mailhost.tcs.tulane.edu
Bianchi, T. Tulane University, tbianch@mailhost.tcs.tulane.edu
Wetzel, R. University of Alabama, rwetzel@biology.as.ua.edu
Tarr, M. University of New Orleans, matcm@uno.edu

 
EFFECTS OF UV RADIATION ON THE COMPOSITION AND MICROBIAL UTILIZATION OF DISSOLVED ORGANIC CARBON (DOC) IN BAYOU TREPAGNIER, LA, USA
 
UV irradiation of DOC in the laboratory can produce small, labile organic compounds utilizable by microbes, but few studies have attempted to document this process in-situ. We examined bulk chemical composition of natural and laboratory-irradiated DOC from shaded (150 micromol/m^2*s average light in surface water) and open (1500 micromol/m^2*s) sites in a bayou with high DOC (30 mg/l). We focused on high-molecular-weight colloidal organic carbon (COC), which is highly photochemically reactive and readily characterized using solid-state C-13 NMR. NMR reveals a dominance of aliphatic and carbohydrate-like carbon with subtle differences in functional groups between COC from naturally shaded and open regions of the bayou and between laboratory irradiated and non-irradiated COC. NMR also revealed slight differences in COC irradiated with and without UV-B. A field mesocosm experiment was conducted in waters irradiated in enclosures at the open (with and without UV-B) and shaded field sites for 8 hours. Bacterial protein productivity (BPP) and abundance were measured for in-situ bacterial cultures grown in COC collected from these waters. BPP per cell was significantly higher in both open treatments than in the shaded treatment (p<0.05), suggesting that bacterial growth may have been enhanced by protection from UV-B and/or by photochemical production of DOC substrates.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS33TH0749S