BIOLOGICAL INFLUENCES ON MINERAL DEPOSITION 

 AT DEEP-SEA HYDROTHERMAL VENTS 



S. Kim Juniper, Verena Tunnicliffe, and A. R. Fontaine 

 Department of Biology, University of Victoria 

 Victoria, British Columbia 

 CANADA V8W 2Y2 



ABSTRACT 



The intimate association of biological and mineral 

 deposition processes at hydrothermal vents in the northeast 

 Pacific provides opportunity for study of their interaction. 

 Three on-going investigations are reviewed. 1) Iron encrustation 

 on vestimentiferan tubes appears to be initiated by iron- 

 accumulating sheathed bacteria that colonize tube surfaces. At 

 one site growth of such encrustations within clumps of tube worms 

 leads to the formation of mini-spires of iron oxide. 2) Mucus 

 secreted in large quantities by an alvinellid polychaete 

 accumulates mineral particles and trace elements. Mucous tubes on 

 smoker chimneys may affect chimney growth by reducing wall 

 porosity. 3) Examination of filamentous iron/silica deposits 

 formed from sulf ide-depleted fluids suggests that their formation 

 may depend on the prior existence of filamentous bacterial mats. 

 Mineral deposition on biological surfaces is potentially 

 deleterious to most vent organisms, although encrustations on 

 vestimentiferan tubes may protect them from predation. While 

 many mechanisms of bio-enhancement of mineral deposition are 

 becoming apparent, their overall quantitative significance 

 remains to be determined. 



INTRODUCTION 



The hydrothermal vent environment is a milieu of intense 

 geochemical activity where oxidation/reduction reactions lead to 

 the precipitation of sulfide, sulfate and oxide minerals. Most 

 activity is confined to a narrow zone near hot water openings 

 where element-rich hydrothermal fluid mixes with ambient 

 seawater. This same zone bounds a unique ecosystem driven by 

 energy released in the oxidation of H^S and other reducing 

 substances present in venting fluids. In their exploitation of 

 hydrothermal fluids vent organisms create structures and produce 

 debris that alter the vent f luid/seawater mixing regime and form 

 a complex mosaic of microenvironments (Juniper 1988, Tunnicliffe 

 et al. 1985). A recent study by Johnson et al . (1986) suggests 

 that the metabolism of vent organisms ( Vestimentif era ) can 

 significantly influence geochemical gradients around vent 

 openings. Such passive and active biological effects on 

 geochemical processes are of interest to the earth sciences as 

 they can influence the formation of mineral deposits. 



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