Spatial and temporal distributions of dominant epiphytes on the stipes of Laminaria hyperborea (Gunn.) Fosl. (Phaeophyta:Laminariales) in S.E. Scotland

The epiphytic flora of the stipes of Laminaria hyperborea (Gunn.) Fosl. at St. Abbs Head, Berwickshire, Scotland has been examined. Four species Palmaria palmata (L.) O. Kuntze, Ptilota plumosa, (C. Ag.) Huds., Membranoptera alata (Huds.) Stackh., and Phycodrys rubens (L.) Batt. make up > 95% of the epiphyte biomass. The species show two distinct patterns of zonation, one with depth the other with respect to position on the host stipe. Palmaria is found on the upper parts of the stipes at 1 and 2 m depth, with the three other species found lower on the stipe. At 6 m depth Ptilota occupies the position on the stipe where Palmaria had occurred in the shallower water. In the deepest samples (12m) Ptilota was absent and its position on the stipe was occupied by Phycodrys and Membranoptera. This zonation is reflected in the biomass of the epiphyte species, Palmaria is restricted to the shallow waters, Ptilota reaches its greatest biomass at intermediate depths while Membranoptera and Phycodrys are most abundant at 6 m and below. Palmaria, Membranoptera, and Phycodrys show similar patterns of seasonal changes in epiphyte biomass with a peak in September and a decline in winter. Ptilota, which in the British Isles is considered to be a species of northern distribution, shows an earlier peak biomass and a correspondingly earlier decline in abundance.