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Microbial Communities in Sediments across the Louisiana Continental Shelf
Citation:
Devereux, R., J. Lehrter, D. Beddick, J. James, B. Jarvis, K. Houghton, D. Yates, J. Aukamp, M. Hoglund, S. Friedman, AND F. Genthner. Microbial Communities in Sediments across the Louisiana Continental Shelf. American Society for Microbiology General Meeting, New Orleans, LA, May 30 - June 02, 2015.
Impact/Purpose:
Describe interrelationships between sediment biogeochemistry and microbial communities at stations located across the Louisiana continental shelf in the northern Gulf of Mexico
Description:
The Louisiana continental Shelf (LCS) is a dynamic system that receives discharges from two large rivers. It has a stratified water column that is mixed by winter storms, hypoxic bottom water from spring to fall, and a muddy seafloor with highly mixed surficial sediments. Spatial variability in LCS sediment biogeochemistry and microbial communities were evaluated in October 2010 at twelve stations located on four shallow (10 m) to deep (50 m) water transects longitudinally spaced across a 300 km expanse. Sediments on transect A, within 25 km of the Mississippi River delta, had the highest concentrations of solid Fe(III) and porewater Mn with low porewater Fe2+ concentrations and low sulfate reduction rates. In contrast, the transect F shallow water station (F04, south from Vermillion Bay) had low solid Fe(III), low porewater Mn, high porewater Fe2+, and high sulfate reduction rates. Because sediment organic matter (OM) concentrations were similarly high (1.5%) along transect A and at station F04, the biogeochemical parameters were consistent with OM decomposition predominantly via Mn(IV) and Fe(III) reduction pathways along transect A and through sulfate reduction at station F04. Microbial community composition was investigated at six stations using genomic DNA extracted from 45 surficial sediment samples, PCR amplification of the 16S rRNA gene HV4 region with universal primers, followed with Ion Torrent DNA sequencing. Microbial communities clustered by station on the basis of a shared species analysis, and in some instances by depth within a station. Desulfobulbus spp. and Desulfobacteriales abundances were nearly twice as high at station F04 (2.2 and 2.9% of the total, respectively) than at transect A shallow station A02 (1.2 and 1.7%) consistent with biogeochemical measurements indicating the importance of sulfate reduction at F04. Differences in abundances of putative iron reducers between sediment samples have yet to be discerned. Archaeal sequences represented 2.5% of the sequences obtained with those of thaumarchaeota Marine Benthic Group-I being the most prevalent. Shared species analysis generated clusters of archaeal communities by depth more so than by station. These results show that LCS sediments harbor a mosaic of microbial communities shaped by location and biogeochemical parameters.