Shallow-Water Benthic Communities on California's Outer Continental Shelf

Abstract

Benthic macroinvertebrates and macrophytes were studied at depths from about 20 to 30 m on Cortes and Tanner Banks, 180 km offshore from San Diego, California, USA. The structure of these communities is described in terms of percentage cover, biomass, species diversity, and species evenness. Two distinctly different communities were present. The shallow-water community was best developed above 25 m depth, and dominated by the southern sea palm Eisenia arborea which formed dense stands on ridges and pinnacles. The community below 30 m was characterized by the encrusting red coralline alga Lithophyllum proboscideum. Remote from shore and weather-beaten, Cortes and Tanner Banks harbor subtidal communities whose relative species abundances differ from those of comparable depths near the southern California mainland and Channel Islands.