Chapter 2 - Geothermal steam vents of Hawai’i

Abstract

Steam vents and caves are abundant on the island of Hawai’i. In contrast to terrestrial geothermal fields, few if any flowing springs or bubbling pools are present. Steam vents represent the most abundant feature of all geothermal fields both on islands and in terrestrial areas. We describe two newly identified chemical types of sulfur and nonsulfur steam caves/vents. This new type of steam cave has abundant salt deposits containing unknown microorganisms that remain to be isolated and characterized. This study also includes a chemical characterization of solid surfaces comprising steam deposits and condensed steam in (1) sulfur-based caves, (2) iron/sulfur habitats, and (3) nonsulfur sites. While we were able to readily isolate DNA from steam deposits in some cave sites, challenges still remain using traditional methods for DNA isolation and commercial DNA kits. In the process of improving DNA isolation methods, we discovered ammonia-oxidizing archaea in a few different steam cave locations on the island and were able to correlate these to site-specific chemistry through the analysis of condensed collected steam and steam deposits, showing that the putative necessary nutrients were present in relatively high amounts in Hawaiian steam caves. Overall, we present genetic and microbiological studies that point to a deep richness and diversity of a largely unknown and understudied extreme habitat that represents a rich source of novel bacteria and archaea, which remain to be identified.