Epífitos de las hojas de Posidonia oceanica: variaciones estacionales y batimétricas de biomasa en la pradera de las islas Medes (Girona}

Abstract

B iomass seasonal variation of leaf epiphytcs of Posidonia oceanica along a depth gradient in Medes Islands (NE Spain). Biomass seasonal variation of the epiphytes of the mediterranean seagrass Posidonia oceanica was studied by means of a bi-weekly sampling programo Maxima, up lo 0.5 gdw/shool (270 gdw/m2 of sea bOllom) are evident in summer all along the depth gradient. A second maximum, in spring, is delecled in the shallower stations. The former corresponds lo the encrusting Rhodophyta-dominated community, while the latter corresponds to another assemblage dominated by Phaeophyta. 1he relation between epiphyte biomass and sorne biological features of Posidonia was statistical1y investigaled. From a multiple linear regression model, it is concluded thal the summer community is the endpoint of a succesion interrupted by leaf faU in early autumn, while the spring one is rather photophilic and represenls a seasonal aspecl of the communiLy.