Threat to macroalgal diversity: effects of the introduced green alga Caulerpa racemosa in the Mediterranean

摘要: Caulerpa racemosa is a tropical green alga introduced into the Mediterranean probably as an immigrant from Red Sea. This study evaluated modifications caused by C. invasion on structure of benthic macroalgal community near Leghorn (northwestern Mediter- ranean). To achieve this objective, we studied algal assemblages 2 dif- ferent substrata monitoring phytobenthic before and after inva- sion comparing our results with not invaded racemosa. Results showed that invasive completely covered surface both types substratum 6 mo start invasion. With rapid horizontal elongation stolons (up to cm d -1 ) overgrew native species within 4 mo. As consequence, phyto- deeply changed: cover, number diversity greatly decreased. Furthermore, relative importance among vegetation layers assem- blage turf encrusting were affected while erect survived 1 yr During period December May, when cover biomass diminished, did return initial conditions. Instead, structural changes increased in following season, indicating local scale.