difference which has been attributed to the amount and rate of 

 food supply. The biomass (expressed as wet weight) of animals at 

 most vent ecosystems can exceed 20-30 kg m - ^ (Hessler and 

 Smithey 1983, Laubier and Desbruyeres 1984). Although the list 

 of characteristic vent organisms continues to grow, at least 40 

 new species from 16 previously unknown families of invertebrates 

 have now been described (summarized by Grassle 1985, 1986). In 

 addition to these predominantly sessile benthic organisms, there 

 is also a vent-associated fish fauna (Cohen and Haederich 1983); 

 however, the vertebrates as a group display a lower degree of 

 endemism than that observed among the invertebrate fauna. 

 Despite the ubiquitous presence of animal communities at deep-sea 

 vents, their distribution and abundance is far from uniform. 

 Distinct zonation patterns, perhaps in response to the 

 physical/chemical characteristics of the discharged hydrothermal 

 fluids, are commonly encountered (Hessler and Smithey 1983; 

 Tunnicliffe, Juniper and de Burgh 1985). 



Another feature of the hydrothermal vent communities is the 

 large difference in relative abundance of dominant organisms 

 occurring in otherwise similar habitats. For example, at the 

 Galapagos Rift spreading center, several characteristically 

 different ecosystems, each dominated by a different vent species, 

 have been observed along a 10-20 km segment of the rift zone 

 (Galapagos Biology Expedition participants 1979). A similar 

 observation was recorded for several individual hydrothermal vent 

 fields along a 1 km portion of the Explorer Ridge (Tunnicliffe, 

 Botros, de Burgh, Dinet, Johnson, Juniper and McDuff 1986). 



Pele's Vent field and other hydrothermal areas on Loihi 

 Seamount are in conspicuous contrast to other characteristic 

 deep-sea vents by the absence of a luxuriant benthic community. 

 Although it is conceivable that a Loihi vent-associated benthic 

 community actually does exist but has thus far eluded both the 

 saturation bottom photography surveys (Malahoff, McMurtry, 

 Wiltshire and Yeh 1982; A. Malahoff and R. Grigg, pers. comm. ) 

 and the Alvin and Pisces V dive tracts, a more probable 

 conclusion is that a Loihi Seamount vent community is, in fact, 

 absent . 



This is of particular interest because bacterial 

 populations, which presumably comprise the base of other deep-sea 

 hydrothermal vent food webs, are present in high concentrations 

 at Pele's Vent. It has been suggested that submarine 

 hydrothermal activity may be too infrequent to support a 

 specialized benthic community of animals (Malahoff, McMurtry, 

 Wiltshire and Yeh 1982); however, it is now well known that the 

 communities at other hydrothermal vent sites have evolved in 

 spite of discontinuous venting and variable hydrothermal fluid 

 discharge. 



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