The third and hottest water sample, Stevenson Island 72, comes from a deep trench east of Stevenson Island in the central portion of the lake, where small, well-developed hydrothermal vents coalesce along northwest-trending deep fissures that reach maximally 133 m depth, the deepest point in the lake (Morgan et al., 2003b).
The fourth sample, West Thumb Canyon 129, represents hot vent water from a sublacustrine explosion crater in the western part of West Thumb basin, in the westernmost part of the lake (Morgan et al., 2003b).
Total DIC was analyzed by the Teflon-membrane flow injection method of Hall and Aller (1992), in which the sipper tube was inserted through the three-way valve and the syringe plunger used to prevent formation of headspace during injection.
For deep samples from Stevenson Island, unavoidable degassing effects were reduced by shaking the syringe thoroughly just before sipping, as the method measures all forms of CO including dissolved gas.
Direct observations by SCUBA and ROV have revealed a wide range of hydrothermal features, including large hydrothermal chimneys; gas fumaroles; seepage of hot, shimmering water; and sulfur-oxidizing microbial mats growing around hot water seeps and vents (Remsen et al., 2002).
Examination of an ancient vent chimney revealed internal conduit structures with metal sulfide precipitates, indicating long-term hydrothermal activity (Cuhel et al., 2004). Rubber-free all polypropylene (PP) syringes with three-way valves were used to collect water from the 2-L ROV-mounted piston syringe samplers without introducing headspace. The ROV’s screw drive was used to squeeze the water into receiving syringes to maximally retain dissolved gases. Reduced sulfur compounds (hydrogen sulfide, thiosulfate, sulfite) were quantified by a scaled-up modification of the microbore high-performance liquid chromatographic (HPLC) method of Vairavamurthy and Mopper (1990), using dithio-bis-nitropyridine (DTNP) derivatization. Samples were collected in PP syringes and after rinsing, exactly 10 m L were squeezed through 0.2 μm nylon syringe filters (Whatman Acrodisc) into acid-washed 20 m L liquid scintillation vials (LSV). nov., an extremely thermophilic, facultatively heterotrophic, sulfur- oxidizing bacterium from Yellowstone National Park, and emended descriptions of the genus Sulfurihydrogenibium, Sulfurihydrogenibium subterraneum and Sulfurihydrogenibium azorense. The fifth sample from the West Thumb Basin, West Thumb 98, represents a cooler, low activity water sample from the West Thumb area. In situ temperatures measured by ROV, and chemistry of the syringe-sampled waters are shown in Table 1. Analytical equipment was transported to Yellowstone National Park and set up as a field laboratory at the National Park Service Lake Station. Freshly collected samples for stable analytes were filtered through 0.2-μm filters (Supor-200, Pall Corp.) and aliquoted for the different analyses. Hydrothermal vent waters were collected in July 2003 from five locations (Table 1) in Yellowstone Lake for microbial community analysis by 16S r RNA gene sequencing (Table 1). The first two samples come from the Mary Bay area near the northeastern shore of the lake, one of the hydrothermally most active areas of Yellowstone Lake, with high heat flux and numerous hydrothermal vents (Morgan et al., 2003b): Mary Bay West 12 is a surface water sample taken above a nearshore bubbling warm fumarole in shallow water (1 m), and Mary Bay Canyon 28 represents warm deep water (52 m) below the sill of an underwater canyon in Mary Bay.