, Volume 122, Issue 1, pp 13-21

Floating clumps of seaweed around Iceland: natural microcosms and a means of dispersal for shore fauna

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Macrofauna in 41 clumps of floating seaweeds taken up to 117 km from the shore of Iceland between 1990 and 1992 was examined. Thirty-nine taxa were found. Many of the species inhabit seaweed on the shore or live in cast-up algae, but some benthic/epibenthic and planktonic/neustonic species were also common. The macrofauna communities of floating clumps were shaped both by colonization from the surroundings and the disappearance of individuals carried from the shore and included species rarely found elsewhere. A positive correlation between density of individuals and size of clumps was found for many species, while there was a negative correlation between density of individuals and distance from shore in some species. Species richness was positively related to clump size. Number of species per clump declined with distance from shore, while the expected number of species per ten individuals did not. Results indicate that rafting on floating seaweed is a mechanism whereby many intertidal animal species can be dispersed over long distances, possibly hundreds of kilometers or more.

Communicated by T. M. Fenchel, Helsingor