Redox Speciation and Distribution within Diverse Iron-dominated Microbial Habitats at Loihi Seamount

Deep-sea hydrothermal systems such as the Loihi Seamount hydrothermal field are important examples of environments where both chemical and biological oxidation of Fe can occur simultaneously, and provide an ideal system to study the speciation and distribution of redox-sensitive bio-reactive elements such as Fe, Mn and S. A total of 13 discrete ROV dives were conducted within the Loihi Summit area over three cruises in 2006, 2007, and 2008. Here, we present and compare data from 17 distinct sites of historical and current interest, from focused and diffuse hydrothermal flow localities, over the three-year sampling period. We coupled an in situ electrochemical analyzer (ISEA) to a sensor wand and a high-resolution in situ micromanipulator deployed from ROV Jason-II to measure dissolved redox species within hydrothermal fluids and microbial mats at Loihi Seamount in complement to analyses on discrete samples collected using Titanium samplers. We compare in situ electrochemical data with traditional geochemical sampling and analysis techniques, and provide a geochemical context for past, on-going, and planned microbial ecology studies.