9 Beyond biogeography: large‐scale patterns of distribution and abundance of intertidal marine algae along the us west coast

Abstract

Biogeographers have long been intrigued by the richness and diversity of the Northeast Pacific algal flora. Most studies have focused attention on distributional patterns delineated into provinces and most strongly influenced by temperature. However, biogeographical studies have always been plagued by the necessity of interpreting distributional data that may be incomplete, non‐quantitative, limited in spatial extent and taxonomic resolution. We attempt to overcome some of these impediments by providing a quantitative description of intertidal community structure across a large spatial scale; ranging from northern Washington to southern California, including the California Channel Islands. We quantified patterns of distribution and abundance of marine algae and invertebrates in permanently marked grids extending 30 m along the shoreline and vertically from the upper barnacle zone to the surfgrass zone at MLLW. We identified most organisms to species level, when possible and collected voucher specimens of all taxa. Here we present the results of these studies focusing on geographic patterns of algal richness and diversity, patterns of abundance across geographical ranges, and functional group abundances relative to regional and mesoscale oceanographic patterns.