Molluscan assemblages associated with photophilic algae in the Marine Reserve of Ustica Island (Lower Tyrrhenian Sea, Italy)

Very few studies have addressed the effect of protection on macrozoobenthos in marine protected areas, and particularly for sites in the Mediterranean Sea. In the present study, the molluscan assemblages associated with photo philic algal communities of the Marine Reserve of Ustica Island, were inves tigated. A survey was carried out along transects from 1 tr, 15 m in depth, during the spring of 1996 at three different sites, subjected to different levels of reserve protection. Species richness and number of individuals r eflected the level of protection, and both variables were significantly hig her in the integral (most heavily protected) part of the reserve compared w ith the less well protected buffer areas. Species diversity values showed n o correlation with the level of protection. The results reported here do no t agree with previous findings on the 'reserve effect' involving large-size d macrozoobenthic species. However, the data reported, together with a stud y on polychaetes from the same study sites, and visual census observations concerning the fish assemblage of the island may support the hypothesis tha t protection of piscivore and macrocarnivore species within the integral re serve suppresses populations of small-sized microcarnivorous fish species, allowing 'prey-release' of small benthic invertebrates.