Trans-Atlantic rafting by the brooding reef coral Favia fragum on man-made flotsam

Abstract

Specimens of the brooding reef coral Favia fragum were found on man-made flotsam stranded on the North Sea shore of the Netherlands. Based on the associated epifauna originating from the southeast USA, we estimate that the corals must have crossed the Atlantic Ocean, transported by the Gulf Stream and the North Atlantic Drift. The size of the corals suggests that they might have had enough time to cross the Atlantic alive and that they already reached the age of possible self-fertilization before they entered waters that were too cold to survive. The temperature requirements and the presently known geographic range of F. fragum are compared with Atlantic summer and winter isotherms and oceanic currents in order to project a hypothetical northernmost range boundary. With increasing pollution, man-made flotsam may become a progressively more common substrate for reef corals that depend on rafting for long-distance dis persal. Eventually, with warming seawater, floating debris may cause tropical marine species to expand their distribution ranges towards higher latitudes. © Inter-Research 2012.