Hydrocarbons Associated with Fluid Venting Process in Monterey Bay, California

by T. D. Lorenson, K. A. Kvenvolden, F. D. Hostettler, R. J. Rosenbauer, J. B. Martin, and D. L. Orange

Introduction

The Monterey Bay National Marine Sanctuary encompasses about 14,000 km2 of marine waters along the central coast of California. The centerpiece of this sanctuary is Monterey Bay which is underlain by a network of deep submarine canyons.

We have begun a multifaceted study to describe and interpret the hydrocarbons in surface and near-surface sediment of the sanctuary in order to define the hydrocarbon background and to describe the processes responsible for the hydrocarbon occurrences. Of special interest are the presence of chemosynthetic communities nestled in areas of fluid venting.

Fluid venting in the deep ocean supports chemosynthetic 'cold seep' ecosystems and may play an important role in world-wide, deep ocean ecology and element cycling. At the base of the food chain are hydrocarbons fueling the process in a world devoid of light.

A chemosynthetic 'cold seep' ecosystem occurs at a site 1,000 m deep and is interpreted as the surface expression of a mud volcano on Smooth Ridge near Monterey Canyon. Sediment samples from within and near cold seeps on Smooth Ridge were collected by push cores, using a Remote Operated Vehicle (ROV).