Identity and abundance of diverse diazotrophs inside and outside six geochemically distinct cold seeps

In the present study, we investigate the identity and abundance of diazotrophs within sediments collected along distance gradients from inside to outside six cold seeps from two geologically distinct regions: Shallop Canyon East, Shallop Canyon West, New England, and Veatch Canyon on the passive U.S. Atlantic Margin; and Clam Field and Extrovert Cliff in the Monterey Bay Fault Zone. While the passive margin seep system contains a variety of methane concentrations and classic cold seep communities, the Monterey Bay seeps contain high concentrations of both methane and non-methane hydrocarbons, as well as methylotrophic substrates, with very few ANME archaea. By combining high-throughput amplicon sequencing of nifH, a taxonomy-inferring and homolog-detecting pipeline, and real-time qPCR, we attempt to characterize diazotrophic populations at these six cold seeps.