Characteristics of a hydrothermal vent assemblage on a volcanically active segment of Juan de Fuca Ridge, northeast Pacific

Abstract

An eruption on Cleft segment, Juan de Fuca Ridge, in 1986 provided an opportunity to observe potential successional patterns in vent-animal colonisation. Other objectives were to describe the Cleft fauna, examine the distribution and abundance of selected taxa, and determine if the fauna reflected changes in water chemistry. Biological samples were tubeworm grabs collected by submersible, and visual data were still photographs and videos. Two years post eruption, there were extensive diffuse vents and 23 of the 44 species constituting the Cleft species pool were present. Five years post eruption, most low-temperature vents were extinct. High-temperature venting was maintained, and biological communities were reduced in visual extent. Four of the 44 species in samples from 1988-1994 accounted for over 90% of the individuals. Cluster analyses of species collected on tubes did not distinguish year or substratum differences, suggesting that a study of less than a year is necessary to document successional patterns at new vents. The Cleft subset of the Juan de Fuca Ridge species pool is likely adapted to episodic eruptive events on the decadal scale. Major changes in fluid chemistry did not result in detectable community changes other than habitat loss due to a decrease in dissolved sulphide availability.