RAPID DEVELOPMENT OF BIOLOGICAL COMMUNITY STRUCTURE AND ASSOCIATED GEOLOGICAL FEATURES AT HYDROTHERMAL VENTS AT 9-10 NORTH, EAST PACIFIC RISE.

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RAPID DEVELOPMENT OF BIOLOGICAL COMMUNITY STRUCTURE AND ASSOCIATED GEOLOGICAL FEATURES AT HYDROTHERMAL VENTS AT 9-10 NORTH, EAST PACIFIC RISE.

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Title: RAPID DEVELOPMENT OF BIOLOGICAL COMMUNITY STRUCTURE AND ASSOCIATED GEOLOGICAL FEATURES AT HYDROTHERMAL VENTS AT 9-10 NORTH, EAST PACIFIC RISE.
Author: Shank, TM; Fornari, DJ; Edwards, M; Haymon, R; Lilley, M; Von Damm, K; Lutz, RA
Abstract: The discovery of newly formed hydrothermal vents in April 1991 at areas of recent volcanic activity between 9O45' and g052'N on the Eat Pacific Rise (EPR, depth 2500m) afforded the first opportunity to follow initial biological and geological changes at a number of deep-sea hydrothermal vents. Photographic images taken by the ARGO optica acoustical system in 1989 had documented well-developed vent communities just sixteen months prior to this discovery. During the course of a submersible dive series in 1991 it became apparent that ongoing eruptions had caused dramatic alterations in the dism'bution and character of the vent faunu since 1989. nese observations, using the DSV Alvin during the eruptive period (April 1991), revealed expansive areas of newly formed terrain extensively draped by 10 to 20cm thick mats of colonizing bacteria Several areas were characterized by scorched vestimentiferan tissue, burnt and broken mussel shells, and beak of mussels overrun bypesh lavaljlows. Hydrothemal vent jluid in excess of 4OO0C was recorded and sampled. Sulphide-laden "black smoke11 was observed emanuting fiom bare basalt, whereas hydrogen sulphide concentrations were an order of magnitude higher than ever recorded with pH's of 2.6. As a result of this discovery, 210 specially designed polyethylene markers were deployed along a 1.37 km segment of the Axial Summit Caldera (ASC) of the EPR between 9O49.61' and g05O.36'N in March 1992. This transect, which traverses numerous active high temperature vent j?eldi (300-403Â C) and zones of low temperature dime jlow (15-35O C), was extensively documented utilizing a variety of optical imaging systems. Data has been collected from over 16,400 still 35 mm images, 215 hours of 8 mm and Hi-8 mm video, and 2400 electronic still camera (ESC) images. Photographic, chemical and temperature duta obtained during five field programs that took place before, during, 11 months, 32 months, and 35 months after the 1991 volcanic event have enabled us to assess temporal changes in geological features, vent $uid geochemistry and biological communi~ structure. To &te our field studies have documented: 1) the dramatic colonization of large, thriving populations of reproductively mature Rifia pa(;h~utila where previously there hud been only small, sparsely distributed clumps of Tmia je&honanq 2) the rapid growth of several new su&& chimneys 7-10m in height, and 3) the esfi:lblishment of robust hydrothermal communities including the prolveration of brachyuran and galatheid crabs, zoarcid j%h, and swarming amphipoh. l?ze serrendipitous discovery of a volcanic eruption in April 1991 has provided, for the jirs,t time, the opportuniq to document temporal and spatial changes in hydrothermal vent cornmuniq structure fiom the apparent origination of several deep-sea hydrothermal vents. l%t?se observations have profoundly altered the conventional perception of timescales on which biological processes operate as deep-sea hydrothermal vents.
Description: American Academy of Underwater Sciences (http://www.aaus.org/)
URI: http://archive.rubicon-foundation.org/4947
Date: 1994

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