Composition, abundance, and phenology fF foliose red algae associated with two central California kelp forests

Abstract

Seasonal variations in biomass and reproductive phenology of red algae were studied in two central California kelp forests with different physical environments. At each site, random 0.25-m 2 samples of foliose red algae were collected monthly and biomass (g dry weight) and reproductive condition recorded for each species. At the more protected, rocky site, the perennials Botryocladia pseudodichotoma (Farl.) Kyl., Gigartina corymbifera (Kutz.) J. Ag., and Rhodymenia californica var. califomica Kyl. were most abundant. At the more exposed site with moving sand, both perennials ( Gigartina corymbifera and Rhodymenia pacifica Kyl.) and annuals such as Polyneura latissima (Harv.) Kyl., Phycodrys setchellii Skottsb., and Nienburgia andersoniana (J. Ag.) Kyl. were abundant. At both sites, the biomass of female and tetrasporic plants was generally very low relative to the total biomass. Reproductive plants at the protected site occurred from March to October whereas various species were reproductive at different times during the year at the exposed site. Several interacting factors appear to regulate red algal composition and abundance in these kelp forests. Overstory development, lack of disturbance, and invertebrate overgrowth seems most important at the protected site whereas physical disturbance in the form of sand and water movement appear to be more important at the exposed site.