With reef ecosystems, it may be all or nothing
By DAVID JOLLY
4 March 2012 There might just be something to the idea of marine reserves, a recent survey of the Mediterranean Sea suggests. Scientists led by Enric Sala, a National Geographic explorer-in-residence and a marine ecologist with the Center for Advanced Studies of Blanes in Spain, studied rocky reefs around Mediterranean shores, comparing places that ranged from strictly enforced “no-take” marine protected areas to open-access sites accorded no protection at all. The results, they said, showed a “remarkable variation in the structure of rocky reef ecosystems,” with three distinct groups: reefs with large fish biomass and algae, the healthiest sites; sites with fewer fish, though with an abundance of algae; and reefs with both few fish and “extensive barrens.” They concluded that the only significant variables correlating to the state of life on the reefs was the level of protection accorded to the area and the degree of primary production, mainly photosynthesis by marine plants. The authors concluded that, perhaps not surprisingly, the most strictly enforced no-take areas had the highest fish biomass. But they also found “no significant differences between multi-use marine protected areas (which allow some fishing) and open access areas at the regional scale.” That conclusion suggests that it may be all or nothing, as far as marine protected areas go. “We found a huge gradient, an enormous contrast,” Mr. Sala told The National Geographic. “In reserves off Spain and Italy, we found the largest fish biomass in the Mediterranean.” “Unfortunately, around Turkey and Greece, the waters were bare,” he said. The presence of apex predators — a litmus test for ecosystem health, since big fish must eat many small ones — was found at the Medes Islands Marine Reserve, set aside by the Catalonian government as a protected area almost three decades ago. […] As I noted last week, scientists and conservationists are calling for the creation of a massive system of reserves in the Southern Ocean around Antarctica. Perhaps studies like this one will help to guide the stakeholders when they sit down later this year to discuss the fate of that fragile ecosystem.
