B047-0010
Investigating Subsurface Biogeochemistry in Tide-Impacted Altamaha River Sediment Using Microbial Metagenomics and Metabolomics

Thursday, 10 December 2020
Poster
Kadir Bice1, Kelly Wrighton2, Rebecca Daly2, LeAundra Schöpflin2, Robert Edward Danczak3, Hyun-Seob Song4, John Schalles5 and Christof D Meile1, (1)University of Georgia, Marine Sciences, Athens, GA, United States, (2)Colorado State University, Soil and Crop Sciences, Fort Collins, CO, United States, (3)Pacific Northwest National Laboratory, Biological Sciences, Richland, WA, United States, (4)University of Nebraska Lincoln, Biological Systems Engineering, Lincoln, NE, United States, (5)Creighton University, Department of Biology, Omaha, NE, United States
Abstract:
Tidal river sediments are microbial hotspots due to continuous exchange driven by river discharge and tidal forcing. In these environments, subsurface biogeochemistry revolves around complex organic compounds and microbial communities that interact with these compounds. To investigate these interactions, we integrate metabolomic and metagenomic data collected from a tidally impacted freshwater site at Hammersmith Creek (Altamaha River, GA, USA). Surface and porewater samples were collected over a 48-hour period as part of the WHONDRS initiative, analyzed using FTICR-MS and sequenced at JGI.

The metabolomic data was binned to reduce complexity, and for each bin reactions representing respiration to CO2 were formulated. Reaction rates were estimated following l-theory (Song et al., 2020. doi:10.1101/2020.06.29.177501), accounting for the energetics. Sequencing data has been processed in KBase (MEGAHIT, MetaBat) for assembly and binning; DRAM (Schaffer et al., 2020. doi:10.1101/2020.02.27.968669) assessed the functional capacity of the microbial community.

From porewater and surface water metagenomes we reconstructed 56 medium and high quality metagenome assembled genomes. Preliminary results suggested that both pore and surface water samples were dominated by members of the Gammaproteobacteria, while member of the Patescibacteria and Actinobacteria were cosmopolitan in pore and surface waters, respectively. Annotations showed that microbial communities in pore water samples were able to carry out N fixation, denitrification, nitrification, and indicated the capacity for S cycling with functional genes for thiosulfate oxidation and sulfate reduction being present. Surface waters showed similar N and S cycle capabilities, with differences reflecting more oxidizing conditions. FTICR-MS analyses revealed lignin and tannins as important constituents in the DOC, consistent with the prevalence of microbial genes for polyphenolic metabolism.

Next, this information is integrated into the reaction-transport code PFLOTRAN. This allows one to investigate the preferential use of different organic compounds transported through the subsurface, and to constrain the potential impact of tidally influenced pore water flow on sediment biogeochemistry and benthic fluxes.

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