Will Sea Cucumbers save the Reefs?

SUBHEAD: The sea cucumber's feces may be key to saving coral reefs. By Stephen Messenger on 29 January 2012 for TreeHugger - (http://www.treehugger.com/ocean-conservation/sea-cucumber-poo-may-be-key-saving-coral-reefs.html) Image above: A Leopard sea cucumber or Eyed sea cucumber (Bohadschia argus), in Pulau Aur, West Malaysia. From (http://www.colours.dk/anders/diving/echinoderms/seacucumber/seacucumber.html).

With a name and shape more befitting of a salad-topping fruit than an ocean-faring animal, sea cucumbers are arguably one of the most striking species to roam the sea floor -- but their importance to the health of marine ecosystems is proving far more noteworthy than that unfortunate misnomer. According to researchers from the University of Sydney's One Tree Island station, tropical sea cucumber excrement could hold the key to saving the world's great coral reefs from the devastating effects of ocean acidification.

Sea cucumbers typically eat by scavenging the ocean floor for plankton or bits of other organic debris, and in so doing, they wind up swallowing and digesting a fair amount of sand. But, as it turns out, this process facilities a natural process that may be essential for preserving the health of coral by counteracting the pH level drops associated with ocean acidification.

"When they ingest sand, the natural digestive processes in the sea cucumber's gut increases the pH levels of the water on the reef where they defecate," professor Maria Byrne tells Sky News.

Additionally, another beneficial process takes place inside the gut of the humble sea cucumber -- the creation of calcium carbonate (CaCO3), a building block of coral reefs.

"To survive, coral reefs must accumulate CaCO3 at a rate greater than or equal to the CaCO3 that is eroded from the reef," said Prof Byrne. "The research at One Tree Island showed that in a healthy reef, dissolution of calcium carbonate sediment by sea cucumbers and other bioeroders appears to be an important component of the natural calcium carbonate turnover."

In light of ongoing threats to the world's coral reef ecosystems, particularly along Australia's Great Barrier Reef, from ocean acidification as a result of increased carbon emissions, the importance of sea cucumbers to maintaining a healthy balance will doubtlessly be explored further.

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