Metagenomic insights on Microbial Community Composition within Chandeleur Island Louisiana Salt Marsh Ecosystems, July – September, 2015

Oil spills such as the Deepwater Horizon (DWH) disaster can significantly impact biochemical and biological processes in coastal salt marsh sediments imparting short-term and long-term effects on ecosystem functions. We sought to identify functional and biogeochemical factors important for driving denitrification in Chandeleur saltmarsh habitats. Denitrification, a biogeochemical process, is a vital ecosystem service providing considerable ecological and economic value in coastal habitats, particularly in salt marsh ecosystems. Studies focused on the long-term impact of heavy oiling on microbial populations carrying out denitrification in northern Gulf of Mexico (nGoM) marsh ecosystems are surprisingly limited. Using sediment samples from Red Fish Point measured for N cycle flux during Year 1 studies, we embarked on a deep metagenomic survey (microbial structure and function) of Chandeleur Islands (Louisiana) habitats for the purpose of characterizing extant microbial community composition. The specific objectives of this study were to: i) determine if temporal (July-September 2015) changes occur for known denitrifying taxonomic groups, ii) determine the contributions of N cycle flux measurements relative to microbial community composition, and iii) characterize putative functional potential for nitrogen cycling and sulfur oxidation pathways. Analysis of ~1.3 Terabytes of sequences derived from 30 different vegetated and subtidal marsh sediment samples are discussed. Data highlight salt marsh functional and taxonomic biodiversity within a previously oiled marsh ecosystem. The combination of molecular ecology methods to assess microbial biodiversity coupled with biogeochemical measurements provides greater insights into marsh microbial interactions and N cycling five years after the 2010 DWH spill.