Taylor, G. TT.. SUNY, gtaylor@notes.cc.sunysb.edu
Scranton, M. TT.. MSRC, mscranton@notes.cc.sunysb.edu
Iabichella, M. MSRC, iabichella@msrc.sunysb.edu
Chistoserdov, A. Y.. MSRC, chistoserdov@ccmail.sunysb.edu
Madrid, V. M.. MSRC, madrid@msrc.sunysb.edu

 
CHEMOLITHOTROPHY IN THE CARIACO BASIN, A SIGNIFICANT SUBOXIC SOURCE OF ORGANIC CARBON PRODUCTION
 
Significant peaks (0.5-2.5 uM C d-1; 100 m layer) in dark carbon fixation were measured in suboxic waters on 5 cruises in the Cariaco Basin. Integrated carbon production in this layer was 60-122% of primary production. Depth of the layer varied between 250 and 350 m in response to fluctuations in redox interface position and appears to be controlled by supply of oxidant, O2, NO3, Mn3+ or Fe3+. In enrichment experiments with samples from upper portion of chemolithotrophic layer, dark carbon fixation rates doubled when amended with 0.1 mM S2O3, but were unaffected by similar amendments with ammonium. In samples from lower portion of chemolithotrophic layer, dark carbon fixation rates increased by factors of 5-25 and 2.4-2.6 when amended with 12 uM MnO2 and 6 uM Fe2O3, respectively. Results suggest that observed chemolithotrophy is primarily fueled by reduced sulfur species and may rely on nitrate and oxidized Mn and Fe formed above interface for terminal electron acceptors. Phylogenetic analysis of bacterial communities from chemolithotrophic layer suggest dominance of e-proteobacteria (57 of 60 16S rDNA sequences belong to this subdivision). These sequences shared high degrees of homology with bacteria capable of anaerobic sulfur oxidation (e.g., Thiomicrospira denitrificans), supporting biogeochemical data.
 
Day: Wednesday, Feb. 3
Time: 11:45 - 12:00pm
Location: Hilton of Santa Fe
 
Code: SS38WE1145H