Deep-Sea Hydrothermal Vent Communities at 13°N on the East Pacific Rise: Microdistribution and Temporal Variations

The microdistribution of hydrothermal species at seven sites on the EPR near 13°N was studied from visual images taken by the French submersible Cyana in 1982 and 1984. These data were used to construct microtopographic maps of vent fauna and habitat distribution. Our results suggest the existence of two distinct vent faunal assemblages, one found at high-temperature vents and the other at low-temperature vents. Most vent sites contained various proportions of high- and low-temperature habitat and their associated fauna. Comparison of sites between 1982 and 1984 revealed many changes in habitat characteristics, which often had dramatic effects on the fauna. We have recorded significant growth of smokers and their rapid colonization by Alvinella pompejana; noticeable growth and recession of pogonophoran and serpulid populations, apparently related to fluctuations in fluid flow; dramatic regression of predator populations coincident with the disappearance of primary consumer populations. We conclude that this microcartographic approach is a valuable tool for the study of the structure of the hydrothermal vent bio-cenose and for preliminary investigation of the adaptation of vent organisms to their environment and its rapid evolution.