Transfer of marine organisms: a challenge to the conservation of coastal biocoenoses.

1. The global transfer of species across the world’s oceans is an increasing threat to the biodiversity of the sea and particularly of coastal areas: the magnitude of this peculiar aspect of global change and the significance of its effects on ecosystems are currently debated. 2. The paper addresses, with reference to the Mediterranean situation, the main research needs in coastal ecosystem conservation, such as the availability of baseline assessment of native and non-indigenous species (including biogeography, taxonomy and historical records). Studies on the transfer mechanisms and on the predictability of successful settlement by alien species are also important. 3. Finally, management actions applicable to conservation issues are mentioned and discussed