Easter Microplate Expedition

Purpose: The purpose of the expedition is to locate barriers to gene flow among species of hydrothermal vent organisms in the vicinity of the Easter and Juan Fernandez Microplates. Animals collected elsewhere along the East Pacific and Pacific-Antarctic Rise have shown genetic differences that suggest barriers to larval dispersal exist in this region. The microplates are surrounded on the north and south by transform faults and on the east and west by chains of seamounts and cross-axis currents occur in this region, which may prevent the successful transfer of larvae from vent site to vent site. Known vent sites not previously sampled for genetic studies along the southern extent of the East Pacific Rise will be targeted on this expedition. Plan: Sixteen dives are planned with the DSV Alvin from 23°S to 38°S along the East Pacific Rise and Pacific-Antarctic Ridge, weather permitting. The ship R/V Atlantis will depart from Tahiti on March 12, 2005 and transit for 9 days to the first site, at 38°S. After several dives, the ship will progress northward to sites at 26°S and 23.5°S along the east and west flanks, respectively, of the Easter Microplate. If time permits, dives will also be made on the enormous "dueling propagator" rifts south of the Easter Microplate, the ridges around the Juan Fernandez Microplate, and at the Pito Seamount, an active volcanic seamount at 23°S. The ship will arrive at Easter Island on April 6.