The Fate and Implications of Removal of Hydrothermally-Injected NH4+ from Plume Waters

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High levels of ammonia are discharged from hydrothermal vents at sedimented (Guaymas Basin) and sediment-starved ridge systems (Endeavour Segment on the Juan de Fuca Ridge). This ammonia may be an important substrate for the chemolithoautotrophic production of organic carbon, yet little, if any, attention has been focused on understanding the biogeochemistry of this hydrothermally-derived ammonia. For this reason, the principal investigators working in collaboration with a scientist from Florida International University, plan to determine the rate of NH4+ removal and ascertain what fraction of this hydrothermally-injected NH4+ is consumed via oxidation by nitrification relative to assimilation by heterotrophic bacteria. In collaboration with a scientist from the University of Hawaii Biomedical Research Center, the population dynamics of the relevant nitrifying bacteria in an evolving hydrothermal plume will be determined. The principal investigators also plan to assess the contribution of NH4+ oxidation to organic-C production in hydrothermal plumes.