INTERANNUAL VARIANCE IN A SUBTIDAL EELGRASS COMMUNITY

Interannual variance in seagrass community function may confound the r esults of ecophysiological studies, Biomass and productivity of eelgra ss and its associated algal epiphytes are compared for a ''normal'' an d the ''El Nino'' year of 1991-1992. Light was more abundant during th e Fl Nino event (4.9 versus 5.7 h of bright sunshine per day), while m ost nutrients were less abundant. Subtidal eelgrass increased in bioma ss and productivity (218.1 versus 255.8 g dry weight per m(2) and 4.0 versus 5.2 g dry weight per m(2) per day). The epiphytic community sho wed decreased light-saturated photosynthetic rates (1.1 versus 0.84 mg C per gram dry weight per hour) and biomass specific productivity (1. 30 versus 1.14 g C per gram dry weight per day). Epiphyte biomass and areal productivity were not significantly reduced, however. The domina nt epiphyte grazer (Lacuna spp.) increased in biomass, For several of the parameters measured, seasonal pattern as well as mean value change d significantly from one year to the next. This examination of interan nual variance indicates the need for multi-year studies considering ee lgrass community function.