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Biological Treasure Under the Sea

4 August 2003 (All day)
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Hotspots. Red dots mark concentrations of biodiversity off the Americas (left), Hawaii (middle), and Australia (right).

The ocean has biodiversity hotspots that rival the richness and variety of life found in tropical rainforests, according to a new study. As the first worldwide search for such hotspots, the research strengthens the argument for new marine protected areas and pinpoints areas where such no-fishing zones would be most effective.

Many studies on land have located regions that are home to a remarkable abundance of species; that knowledge has been a great boon to conservation efforts. But little work has been done to investigate hotspots of diversity in the open ocean, where species tend to be more mobile. Marine ecologist Boris Worm of the Institute for Marine Science in Kiel, Germany, tackled the problem with Ransom Myers at Dalhousie University in Halifax, Canada, and others as part of a long-term project that has documented dramatic declines in fish and shark species worldwide (ScienceNOW, 14 May).

In a new paper, the scientists analyzed data from fishing boats. They used data of fish caught at depths less than 200 feet recorded by independent observers placed on the boats, and they supplemented that data with boat logbooks. Using two measures of species diversity, they found that hotspots are concentrated between 20° and 30° latitude. Hotspots tended to be closer to shore and near features such as coral reefs, seamounts, and islands. That's because these waters provide a variety of habitats and are rich in nutrients. Computer models suggested that the hotspots are optimal sites for no-fishing zones because they contain many species, but lower numbers of animals than elsewhere, perhaps because of competition between species. Because the catch of fish in these areas was lower, such measures would protect many species but wouldn't cut into the total catch as deeply, the authors argue in their report, published online this week in the Proceedings of the National Academy of Sciences.

But marine ecologist Enric Sala of Scripps Institution of Oceanography in La Jolla, California, and others warn that even targeted marine reserves likely aren't not enough to resuscitate dwindling populations without more stringent overall limitations on fishing.

Related sites
Boris Worm's site
Science article on declining shark populations
Science article on coral reef diversity hotspots

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