Invasive mussels directly threat intertidal vermetid reef: some evidences from a Sicilian MPA

Biological invasions pose a great threat to natural communities. Brachidontes pharaonis is an Eritrean mussel that has accessed in the Mediterranean sea shortly after the opening of the Suez Canal. At the beginning it had a restrained distribution with small local populations along the Israeli intertidal coast. More than a hundred years later it spread westward as far as NW Sicily, colonizing some hyperaline and natural habitats. Previous studies along the Israeli coast have proved that anthropogenic habitat modi#- cations occurring on vermetid reefs may promote the colonization of this invasive mussel causing a reduction of the indigenous mussel Mytilaster minimus. This study focuses on a population of B. pharaonis that has recently invaded some Dendropoma petraeum reefs inside the Capo Gallo-Isola delle Femmine MPA (Palermo, NW Sicily). Inter-annual comparisons (i.e. before and after the B. pharaonis arrival) show negative e"ects #rstly on the coverage and secondly on the density of D. petraeum. Moreover, no evident changes in the receiving habitat were recorded from before to after, thus suggesting that this non-native mussel may represent a direct, although local, threat to vermetid reefs.