Faunal composition and organic surface encrustations at hydrothermal vents on the southern Juan De Fuca Ridge

Abstract

Examination of a small collection of macroinvertebrates from three vents of the southern Juan de Fuca vent field reveals differences between the vents with respect to species composition, species habits, and microbial and metallic deposits on their surfaces. TWo apparently new vestimentiferan species were found, and for the first time the Juan de Fuca palm worm was observed to dwell on smokers. High acidity values recorded in this system may interfere with the process of shell calcification in an archaeogastropod snail. The surfaces of vestimentifer an tubes at two vents are heavily encrusted with microbial and metallic accumulations. Scanning electron microscope, transmission electron microscope, and energy dispersive X ray microanalysis observations show that iron‐based crusts on orange tubes are built from accumulations of an Fe‐rich particle of distinctive size and shape. Morphological evidence is presented for the microbial origin of Fe‐rich particles. Zn‐rich particles found on black tubes are not of microbial origin. We suggest that iron deposition on surfaces in the vent environment is initially biocatalytic but subsequent deposits may build by simple inorganic reactions.