Coral reefs support much more life than previously thought

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Coral reefs are among the most endangered habitats on earth, yet we still do not know just how much life they support, and now recent research suggests that the diversity of organisms that depend on coral reefs is grossly underestimated.

In new research published in the open access journal PLoS ONE, Smithsonian researchers have conducted the first DNA barcoding survey of crustaceans that shelter amongst dead coral.

Samples were taken from the Indian, Pacific and Caribbean oceans at depths of 26-39'. Despite the samples having a total surface area of only 6.3 square metres, there were 525 different species of crustaceans found living on them.

"So much diversity in such a small, limited sample area shows that the diversity of crustaceans in the world's coral reefs - and by implication the diversity of reefs overall - is seriously under-detected and underestimated," said Nancy Knowlton, Sant Chair for Ocean Science at the Smithsonian's National Museum of Natural History and co-author of the survey.

"We found almost as many crabs in 6.3-square meters of coral as can be found in all of the seas of Europe. Compared to the results of much longer and labour-intensive surveys, we found a surprisingly large percentage of species with a fraction of the effort."

DNA barcoding offers scientists a quicker and more efficient method for surveying over the more time consuming traditional methods.

"DNA barcoding provides a standardised, cost-effective method of coming to grips with the staggering diversity of the world's oceans," Knowlton said. "It has enormous potential for use in broad global surveys, allowing us to find out what is living in the ocean now, and to keep track of it in the future."

Scientists collected only those crustaceans they could see, which ranged in size from 0.2 to 1.9" long, and all specimens that had their DNA sequenced were preserved for future examination by taxonomists.

"We collected dead corals because live corals defend themselves from being inhabited by other invertebrates," said lead author Laetitia Plaisance of the Smithsonian's National Museum of Natural History and the Scripps Institution of Oceanography.

"Given the complexity and extent of the world's coral reefs, the survey covered only a very limited depth and habitat range," said Plaisance. "And yet we have so many more species than we ever expected."

For more information see the paper: Plaisance L, Caley MJ, Brainard RE, Knowlton N, 2011 The Diversity of Coral Reefs: What Are We Missing? PLoS ONE 6(10): e25026. doi:10.1371/journal.pone.0025026

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