“…The summit area of L o'ihi (at 1000 m water depth, Fig. 1A) hosts numerous low-temperature (upper range 45-558C) hydrothermal vent systems with fluids containing high concentrations of ferrous iron (Garcia et al, 2006;Staudigel et al, 2010). Since the initial discovery of Zetaproteobacteria (Emerson et al, 2007), numerous studies from around the world have demonstrated their preponderance in various marine environments wherever iron is a likely energy source, including mid-ocean ridges (Toner et al, 2009;Scott et al, 2015), back-arc hydrothermal fields (Kato et al, 2009;Edwards et al, 2011), seamounts (Moyer et al, 1995;Emerson and Moyer, 2002) and coastal/coastal margin habitats (Dang et al, 2011;Rubin-Blum et al, 2014).…”