INVASION DYNAMICS OF THE JAPANESE KELP UNDARIA PINNATIFIDA: IS DISTURBANCE KEY TO THE INVASION PROCESS?

The Japanese kelp, Undaria pinnatifida, is listed among the 100 most damaging invasive species of the world by the World Conservation Union. First discovered in the United Kingdom in 1994, the kelp is rapidly spreading across harbours in the British Isles. However mechanisms by which the invasive species overcomes resistance in native communities and spreads on the natural shore are not well understood. This study examines disturbance as a facilitator of U. pinnatifida invasions by testing the effects of the removal of native canopy forming algae, the removal of turfing and encrusting algae and the removal of the whole algal community on U. pinnatifida recruitment. The invasive kelp recruited almost exclusively in the absence of native canopy forming algae indicating that light availability played a major role in the invasion success of the kelp. A second objective was to examine potential consequences of U. pinnatifida invasion within a biologically generated habitat by comparing epifaunal assemblages inhabiting U. pinnatifida with co-occurring native kelp species. It was found that U. pinnatifida hosted significantly different epifauna assemblages compared to native kelps with lower species abundance and diversity. This study concluded that U. pinnatifida negatively influences an important biological habitat with potential consequences on a broader scale.In collaboration with The Marine Biological Association of the United Kingdo