At the present time there is no data base for comparison of 

 Loihi to other seamounts which lack the volcanically induced 

 disturbance, metalliferous sediment deposition and hydrothermal 

 fluid discharge which characterize our study site. Consequently 

 it is difficult to evaluate whether recruitment, per se, is a 

 factor in the establishment of seamount faunas or whether the 

 depauperate Loihi fauna is directly related to the fact that it 

 is geologically active with a resultant instability of the 

 substratum (Grigg 1988). 



Another possible explanation for the absence of fauna at 

 the Pele's Vent site is the toxicity of the hydrothermal 

 solutions themselves. As discussed previously, the £ CO2 content 

 of the vent waters is in excess of two orders of magnitude 

 greater than ambient bottom seawater. This results in a 

 lowering of the pH to a value of approximately 5.4 (Edmond, 

 Campbell, Palmer, Falkner and Bowers 1987), a value which could 

 be toxic to most invertebrates. The high concentrations of 

 dissolved trace metals (Edmond, Campbell, Palmer, Falkner and 

 Bowers 1987; Sedwick and McMurtry 1987) may also contribute to 

 solution toxicity. Finally, the fact that Loihi Seamount is a 

 relatively young geological feature compared to the mid-ocean 

 ridge habitats also needs to be considered. It is conceivable 

 that Loihi Seamount constitutes a very early stage in the lengthy 

 processes of dispersal, recruitment and natural selection that 

 are required to establish a successful hydrothermal vent animal 

 community. 



CONCLUSION 



In conclusion we have discovered, explored and sampled 

 active hydrothermal vents on the summit of Loihi Seamount, Hawaii 

 at an area referred to as Pele's Vent. The active vent field is 

 characterized by iron-rich nontronite deposits, warm (30°C) 

 hydrothermal fluids, extensive bacterial mats and by the 

 conspicuous absence of large benthic animals. Our initial 

 experiments have revealed the presence of elevated concentrations 

 of reactive Si, NH 4 + , SRP, ZC0 2 and CH 4 in the discharged vent 

 fluids, relative to ambient bottom seawater. Bacteria present in 

 the warm discharged vent fluids were shown to be metabolically- 

 active at temperatures up to at least 60°C. Bacterial methane 

 oxidation potential was also measured in water sampled from 

 Pele's Vent. Bacterial mats observed in certain regions of the 

 vent field are comprised of long filaments coated with Fe 

 precipitates. It is hypothesized that these tubular structures 

 are actively formed by the growth of Fe-oxidizing bacteria. This 

 hypothesis will require a comprehensive in-situ experimental 

 evaluation. In the words of Rison and Craig (1983), "Loihi 

 volcano, born in the shadow of the world's greatest, if least 

 known, mountains has possibly revealed an important secret, but 

 it is young and needs to be understood." We agree with their 



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