Research Technical Report

A Characterization of the Megafauna at Davidson Seamount

Lundsten, L., A.P. DeVogelaere, J.P. Barry, and D.A. Clague (December 2006)

Poster presentation at the 2006 American Geophysical Union Fall Meeting, San Francisco, CA. Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract V13A-0650.

ABSTRACT

Seamounts offer hard substrate, complex habitat, elevated current velocities, and other features that allow for the existence of unique assemblages of organisms, often dominated by long-lived and fragile corals and sponges. Seamount faunas have high rates of endemism with biogeographic patterns analogous to land-based island faunas. Seamount organisms, particularly long-lived deep-sea corals, are particularly vulnerable to bottom trawling and other resource extraction techniques. Davidson Seamount, located 120 km southwest of Monterey, CA, USA, is an example of a relatively undisturbed and pristine seamount habitat. Volcanic in origin, Davidson Seamount was formed 12-16 million years ago atop a fossil spreading center, which produced a unique pattern of northeast trending ridges on the seamount. Remotely Operated Vehicle (ROV) dives at Davidson Seamount were conducted in 2000 and 2006 by a collaboration of scientists, resource managers and educators. Sixteen dives were annotated in detail using MBARI's Video Annotation Reference System (VARS), yielding more than 60,000 biological observations. Over 170 organisms were identified to the lowest possible taxon. The distribution of organisms in relation to the bathymetric complexity of the seamount were analyzed using ArcGIS 9.1 and NOAA's Benthic Terrain Modeler (BTM) to relate faunal distributions to slope, aspect, and bathymetric position. Video transects completed in 2006 were analyzed to quantify species' density and richness. Several new species were observed and collected, and are currently being described by taxonomists. Results of this study indicate that corals and sponges may have species-specific depth distributions with little overlap of large habitat forming phyla. Moreover, substratum type, slope, and aspect are important in determining the distribution of some coral species. This baseline survey is valuable in describing the fauna of Davidson Seamount, has been used in developing essential fish habitat zones where trawling is regulated by the National Marine Fisheries Service, and will be critical in the final determination for the potential inclusion of the seamount as part of the Monterey Bay National Marine Sanctuary.