Despite the rapid expansion of marine protected areas in the Mediterranean Sea, very few studies have addressed macrozoobenthos responses to protection. The aim of this work was to assess and better understand the potential responses of amphipod assemblages in Posidonia oceanica meadows between different protection levels.
Two approaches were used. First, multiscale variability patterns of amphipod assemblages were investigated at the Revellata Bay (France) and the Tavolara-Punta Coda Cavallo Marine Protected Area (TMPA, Italy), over spatial scales spanning five orders of magnitude (~1 m to >100s of km) for two consecutive years. Second, the role of fish predation in affecting amphipod assemblages was evaluated using experimental manipulations of predation intensity.
Amphipod assemblages of P. oceanica meadows were typified by high density and number of species. Our research revealed that amphipod natural variability was great at small and large scales in P. oceanica meadows. At small scales (from ~1 m to ~10 m), this pattern was in relation to both total amphipod density and/or several species densities, which may be explained by behavioural traits of amphipods. At large scale (>100 km), the structure of amphipod assemblages was different between meadows and may be related to hydrodynamic forces.
During this research, a new caprellid, Caprella tavolarensis was discovered and described. The species is close to Caprella liparotensis, but can be clearly distinguished by smaller size, presence of a short rostrum, body elongate and dorsally smooth, absence of serrate carina on the basis of gnathopod 2 and pereopods, mouthparts scarcely setose, absence of fine setae on peduncle of antenna 1 and absence of swimming setae on antenna 2.
At the TMPA, the structure of amphipod assemblages differed markedly among protection levels. Moreover, it was observed lower densities and/or biomasses of several frequent taxa within the fully protected area and outside the MPA compared to partially protected areas. Meadow features account only for a low proportion of the amphipod variability, while predation by fish seemed to be an important factor in structuring P. oceanica amphipod populations.
Overall, this work suggests that full protection at the TMPA is likely to contribute partially (primarily via fish predation) to the observed variability patterns among zones. However, superimposed factors including behavioural traits of amphipod species and surrounding habitats are likely to be also significant. Whether these changes are representative of all fully protected areas and whether those effects are positive or negative to the meadows, are still unknown