Local benthic assemblages in shallow rocky reefs find refuge in a marine protected area at Madeira Island

The patterns of variability in the composition and structure of benthic communities along two depth strata (5 and 10m) and the presence of sea urchins in structuring the subtidal rocky reefs were quantified in a long-established coastal marine protected area (Garajau MPA) and in two size equivalent and contiguous impacted areas (one highly urbanized and other with high fishing pressure) at Madeira Island (northeast Atlantic). Results suggest i) the MPA could be acting as a refuge for local biodiversity, ii) communities from the highly fished area could be suffering an impoverishment of local biodiversity, and iii) communities from the highly urbanized area would be enriched by the establishment of opportunistic species. These findings support that the level of human-pressure likely plays an important role in the composition of benthic communities in this insular ecosystem, although this was more relevant at the shallower stratum where the key grazer Diadema africanum explained 65% of the variance of benthic assemblages. It is suggested that this MPA small dimension and proximity to human impacted areas are limiting the survival of predators of the D. africanum.