Untitled - CNR

Fishery and Sea ResourcesFigure 1: Caulerpa taxifolia (Vahl) C. Agardh is a green alga of tropical origin, commonlyutilized in aquaria. After an accidental discharge, this species is now widespreadalong French, Spanish and Italian Tyrrhenian coasts. (Photo Michelagnoli FoundationArchive)and molluscs. The most well-known exampleis that of Caulerpa taxifolia (Figure 1)that, due to its very high invasiveness hasbeen defined the “killer alga” [4].The intentional or accidental transport ofNIS to new regions now represents one ofthe four greatest threats to the integrity ofworld’s oceans, together with the chemicalpollution of continental origin, the overexploitingof resources and the loss of habitats[5].NIS can cause severe economic damagesin that they impact activities such as aquaculture,fishing and industry. Paradigmaticexamples are the effects caused bythe bivalve mollusc Dreissena polymorpha(the so-called zebra mussel) (Figure 2) andthe European crab Carcinus moenas in theU.S. [6] or by the ctenophore Mnemiopsisleidyi in the Black Sea [7]. Beside this, notalways the addition of non-native speciesnegatively affects the native biota. Accordingto Reise et al. [8], in many casessuch species expand the functioning andservices of the recipient ecosystem, beingcomplementary to the natives, e.g. in thebetter use of resources and the increasingof functional redundancy.In Italy, the issue of NIS introduction hasbecome evident with the appearance of easilydetectable exotic organisms, such as theabove mentioned green alga Caulerpa taxifoliaand the Japanese clam Tapes semidecussatus,which was intentionally introducedfor aquaculture purposes.The incoming of globalization in the marketsdirectly affects the amplification ofthis phenomenon that, however, followsalso natural pathways with dispersion dynamicsknown since hundreds of years.Indeed, recently, in the Mediterranean anorthward expansion of the distributionof tropical species arrived through GibraltarStrait or Suez Canal is occurring, [9]even in Taranto (Southern Italy, Ionian Sea)where subtropical molluscs and fishes aremore and more frequently observed (Figure3).2126