FLOATING CLUMPS OF SEAWEED AROUND ICELAND - NATURAL MICROCOSMS AND A MEANS OF DISPERSAL FOR SHORE FAUNA

Macrofauna in 41 clumps of floating seaweeds taken up to 117 km from t he shore of Iceland between 1990 and 1992 was examined. Thirty-nine ta xa were found. Many of the species inhabit seaweed on the shore or liv e in cast-up algae, but some benthic/epibenthic and planktonic/neuston ic species were also common. The macrofauna communities of floating cl umps were shaped both by colonizations from the surroundings and the d isappearance of individuals carried from the shore and included specie s rarely found elsewhere. A positive correlation between density of in dividuals and size of dumps was found for many species, while there wa s a negative correlation between density of individuals and distance f rom shore in some species. Species richness was positively related to clump size. Number of species per clump declined with distance from sh ore, while the expected number of species per ten individuals did not. Results indicate that rafting on floating seaweed is a mechanism wher eby many intertidal animal species can be dispersed over long distance s, possibly hundreds of kilometers or more.