Concern about the spread of the invader seaweed Caulerpa taxifolia var. distichophylla(Chlorophyta: Caulerpales) to the Western Mediterranean

Abstract

The Australian alien seaweed Caulerpa taxifolia var. distichophylla, after being established along the Turkish Mediterranean coast in 2006, was recorded in Southern Sicily in 2007. Since then local fishermen asked for support to counteract the effects of entanglement of large amounts of the alien strain wrack in their trammel nets, causing the gear to become ineffective. The further northward and westward spread of this new alien strain is believed to be limited by winter temperature. We present novel data confirming that the new alien strain is fully naturalized in the Central Mediterranean and is expanding its range beyond such limit (i.e. the 15°C February isotherm), thus becoming potentially able to colonize the western basin. Based on a preliminary estimation of the effects on native polychaete assemblages, and considering some peculiarities of Sicily (mostly linked to its geographical position in the Mediterranean Sea), the risk linked to the increasing range of distribution of the invasive algae is highlighted.