Biological and geological dynamics over four years on a high-temperature sulfide structure at the Juan de Fuca Ridge hydrothermal observatory

Abstract

An extensive v~deoscopic study of a h~gh-temperature sulfide structure on the Juan d e Fuca Rldge (northeast Pacific) examined temporal variation in vent community distnbution and l ~n k s between faunal and environmental changes V ~d e o imagery was acquired d u l ~n g a total of 5 manned submersible and ROV (remotely-operated vehicle) dive programs between 1991 a n d 1995 The structure was systemat~cally mapped for each year of the study and a serles of analytical tools was developed to quantify changes in biological and geological features and observable flow patterns Results shoiv ( l ) heterogeneous faunal distnbution, characterized by decimeter-scale patchiness and general absence of vertical gladients, (2) apparent links between commun~ty d~stnbution, and environmental features such as fluid flow patterns, substratum and temperature/chemicdl conditions, (3) a significant influence of perturbations on community dynamics, (4) dbsence of d ~r e c t ~o n a l biological succession at the time scale examlned (years) Overall, these observations strongly suggest that many hydrothermal community changes are initiated by gradual and ablupt flow mod~fications Results are compiled in a dynamic succession model for sulfide edifices where community transitions are dnven by flow vanatlons, and by biolog~cal processes operating at sub-annual t ~m e scales CVe conclude by stressing the need for extended momtonng of short-term dynamics in order to understand the relationslup between hydrothermal communities and their environment