What can we learn from dead corals?

A recent study of dead corals suggests that we have seriously underestimated the biodiversity of the world's coral reefs!

The brown bottom half of this coral colony is still alive,
while the upper half covered with scum is dead.

The scientists studied dead corals because "live corals defend themselves from being inhabited by other invertebrates". But once a coral dies its structure becomes covered with algae, sponges, crustaceans, worms, molluscs and other creatures.

Conducting the first DNA barcoding survey of crustaceans living on samples of dead coral taken from the Indian, Pacific and Caribbean oceans, the scientists found 525 different species of crustaceans in samples with a surface area of just 6.3 square meters.

"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 labor-intensive surveys, we found a surprisingly large percentage of species with a fraction of the effort."

The high prevalence of rare species (38% encountered only once), the low level of spatial overlap (81% found in only one locality) and the biogeographic patterns of diversity detected (Indo-West Pacific>Central Pacific>Caribbean) are consistent with results from traditional survey methods, making this approach a reliable and efficient method for assessing and monitoring biodiversity. The finding of such large numbers of species in a small total area suggests that coral reef diversity is seriously under-detected using traditional survey methods, and by implication, underestimated.

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