HR: 1340h
AN: B33A-0845    [Abstracts]
TI: In Situ Chemical Profiling of an Extremely low Temperature Hydrothermal System at Loihi Seamount, Hawaii
AU: * Glazer, B T
EM: glazer@hawaii.edu
AF: University of Hawaii Department of Oceanography, 1000 Pope Rd., 205 Marine Science Bldg., Honolulu, HI 96822, United States
AU: Briggs, R A
EM: briggs@hawaii.edu
AF: University of Hawaii Department of Oceanography, 1000 Pope Rd., 205 Marine Science Bldg., Honolulu, HI 96822, United States
AB: Loihi Seamount is a submarine, active volcano located on the southeast flanks of the Big Island of Hawaii. It is considered to be the youngest volcano in the chain, sharing the hot spot magma chamber with Mauna Loa and Kilauea. Sites of both vigorous and diffuse hydrothermal venting can be found surrounding the pit crater summit (1000m) and on the flanks of the seamount, down to its base (5000m). Vent fluids at Loihi are chemically distinct from other well-studied marine hydrothermal systems and have been shown to be enriched in carbon dioxide, iron(II), and manganese(II), and deplete in sulfur species. The Loihi summit is located within a zone of low oxygen, further enabling elevated iron(II) concentrations and support for a dominant community of iron-oxidizing bacteria. We deployed a sensor wand consisting of up to four voltammetric working electrodes and the ROV Jason temperature probe, and/or a submersible micromanipulator with voltammetric electrodes to provide real time in situ redox characterizations of hydrothermal fluids and geochemical gradients associated with iron-oxidizing microbial mats and flocs. In addition to surveying known areas of warm temperature (10-60 degrees C) venting at the Loihi summit, we performed widespread profiling of a previously undescribed site at 5000m, that exhibits temperature anomalies of just 0.2 degrees C. Extensive iron-oxidizing microbial mats were shown to occur up to 2m in thickness over several hundred square meters. Bottom water oxygen concentrations were near-saturation, and we observed steep gradients at the mat-interface, with little oxygen penetration and iron(II) concentrations of up to 150 micromolar. Our in situ electrochemical analyses provided an efficient and valuable means for directed discrete sampling of hydrothermal fluids and microbial flocs, as well as previously unattainable high spatial resolution geochemical profiles through the mats.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0452 Instruments and techniques
SC: Biogeosciences [B]
MN: 2007 Fall Meeting