Seminar Series 2005

Biogeography of the hydrothermal vents in the vicinity of the Easter Microplate: highlights of the recent DSV Alvin expedition

JENNIFER PADUAN
Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road Moss Landing, CA 95039

Barriers to dispersal for several species of hydrothermal vent organisms have been proposed to exist along the East Pacific Rise (EPR) in the vicinity of the Easter Microplate (~25 degrees S). For many hundreds of kilometers along the EPR to the north of this region, populations of one mussel and two tubeworm species are homogenous genetically, but those to the south are divergent. Their genetics indicate that they became isolated about 4.4 million years ago, which is approximately when the Easter Microplate began to form. In contrast, a few species exhibit little or no genetic divergence across this region, indicating successful gene transfer through this region.

The rift zones of the EPR in this area have the fastest spreading rates of any mid-ocean ridges in the world. There are probably frequent, voluminous eruptions that wipe out vent communities, the topographic highs may be physical barriers to larval transport, and cross-axis currents may wash planktotrophic larvae from the system. Preliminary observations of the geologic setting and of the animals sampled from vent sites through this region will be presented.