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Sunday, May 9, 2021

Sea cucumbers’ role in protecting coral reefs

A new study has highlighted the importance of excrement for protecting coral reefs.

Researchers from the University of Newcastle, Macquarie University, and James Cook University used drones and satellite images to demonstrate the value of sea cucumber droppings on ecosystems.

Sea cucumbers are closely related to sea urchins and sea stars and help support coral growth through a process called bioturbation, in which sea cucumbers supply the sea floor with sediment that contains calcium carbonate, a critical nutrient for coral.

University of Newcastle conjoint associate professor at the School of Environmental and Life Sciences Jane Williamson said a team deployed satellites and drones on Heron Island to observe and count sea cucumbers over 18km2 in the Great Barrier Reef.

“Using satellite data, we then extrapolated these patterns to the entire reef to have an approximate total number of sea cucumbers present,” associate professor Williamson said.

“In parallel, we ran experiments in aquarium facilities to determine how much sediment was passed by individual sea cucumbers on a daily basis.”

The researchers said their study was demonstrative of the need for better protection of the often-overlooked creature, which faced pressures from overfishing due to their high value in Asian markets.

Sixteen species of sea cucumber are classified as either endangered or vulnerable.

University of Newcastle marine scientist and co-author, Dr Vincent Raoult, explained that the creatures were critical to the health of the ecosystem and excrete 60,000 tonnes of coral-feeding sediment annually – the mass of five Eiffel Towers.

“The disappearance of these creatures would have negative flow-on effects to reef ecosystems,” Dr Raoult said.

“Perhaps because they’re seen as boring, they get ignored and the risk is that, as a result, they haven’t been considered an important factor in the ecosystem of coral reefs.

“If we want to have healthier reefs, we can’t just ignore the fact that sea cucumbers are disappearing and focus solely on climate change, even though that is the major threat to coral reefs, we have to make sure that we address other issues such as overfishing as well.

“It’s very hard though for scientists to have a sense of what the loss of a species might be if we don’t know the scale of their role in the ecosystem.”

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