Alien marine macrophytes in transitional water systems: new entries and reappearances in a Mediterranean coastal basin

Three alien macrophytes, Ascophyllum nodosum, Colpomenia peregrina and Polysiphonia morrowii, are reported for the first time from the Mar Piccolo of Taranto (southern Italy, Mediterranean Sea). Two other species, Agardhiella subulata and Codium fragile subsp. fragile that were not, or were sporadically, detected in the basin since their first record in 1987 and 2002, respectively, were also recorded. In the Mar Piccolo, there appears to be a close link between establishment of alien species and the regular import of shellfish for direct sale. To limit the flow of accidental species introductions, a continuous and rigorous control of all the economic activities performed along the coast is recommended through the enforcement of effective laws and an early detection of new introductions.