BIOLOGY OF AN ACTIVE METHANE SEEP ON THE OREGON CONTINENTAL-SHELF

An active sea-floor methane seep is present approximately 20 km off the coast of Oregon, USA, at a depth of 132 m. Preliminary observations in 1989 suggested that biological activity near the seep was high. In analogy to other seeps, we proposed that the methane served as an energy source fueling enhanced biological productivity. In 1990, samples of pelagic and epibenthic organisms were collected near the seep and compared to collections from background sites in terms of abundance of organisms, community composition, and ratios of the stable isotopes of C, N and S. Vertical profiles indicated greater abundances of bacteria in the near-bottom water over the seep, but no enhancements in the abundances of several categories of microzooplankton. The delta(13)C and delta(15)N values of benthic fishes, crustaceans and sediment organic matter were slightly but consistently lower at the seep, indicating that the seep provided a minor source of C and N to the local food web.