A floristic analysis of the marine algae and seagrasses between Cape Mendocino, California and Cape Blanco, Oregon, USA

The biogeographic area between Cape Men- docino, California and Cape Blanco, Oregon in the USA spans over 320 km and is characterized by prominent coastal headlands. This study was a first attempt to pro- duce a current intertidal macroalgal and seagrass species list for this understudied region with basic habitat attrib- utes included. A total of 164 species of marine macroalgae (105 species within 16 orders in Rhodophyta, 32 species within six orders in Heterokontophyta, Phaeophyceae, and 27 species in six orders in Chlorophyta) and two spe- cies of seagrasses (Anthophyta) were identified. The opti- mal habitat for most species was the rocky intertidal in the mid zone ( > 50%), while some species were special- ists in either tidepool and/or sandy habitats (∼20%). Fur- thermore, based on Akaike Information Criterion, our top ranking model suggests that species richness is dependent on zonation, functional grouping and site location. Based on the seven functional group classification, the leathery macrophytes and crusts were the most prevalent at the two capes exposed to higher wave action and upwelling. One near-endemic species (Cumathamnion sympodophyllum), one invasive species (Sargassum muticum), and seven new records for the region were identified.