Coral bleaching is hitting disastrous levels.
Coral bleaching is hitting disastrous levels.

Coral bleaching begs urgent action

IF there was one message to take away from last night's coral bleaching forum, it was that urgent action is needed.

Global Change Institute Healthy Oceans program manager Dr Tyrone Ridgway explained how in 1998 he visited the reef off Cairns, coming face-to-face with horribly bleached coral.

"It made me, as a biologist, very interested and motivated me to try to come back to Australia to work on corals," he said.

Providence Sailing owner Lindsay Simpson had a similar story, first operating her tall ship off Magnetic Island.

"We used to call the magnificent fringing reef around the island a great place to snorkel, and when we started in 2005 it was," she said.

"Towards the end of our time there, last June, we were actually apologising taking people out there."

What is coral bleaching?

  • Many types of coral have a special symbiotic relationship with a tiny marine algae (zooxanthellae) that live inside corals' tissue and are very efficient food producers that provide up to 90 per cent of the energy corals require to grow and reproduce.
  • Coral bleaching occurs when the relationship between the coral host and zooxanthellae, which give coral much of their colour, breaks down. Without the zooxanthellae, the tissue of the coral animal appears transparent and the coral's bright white skeleton is revealed.
  • Corals begin to starve once they bleach. While some corals are able to feed themselves, most corals struggle to survive without their zooxanthellae.
  • If conditions return to normal, corals can regain their zooxanthellae, return to their normal colour and survive. However, this stress is likely to cause decreased coral growth and reproduction, and increased susceptibility to disease.
  • Bleached corals often die if the stress persists. Coral reefs that have high rates of coral death following bleaching can take many years or decades to recover. (To read more visit the GBRMPA website)

Dr Ridgway went on to explain coral bleaching would not only see us lose one of our main tourism drawcards, but the marine life that goes along with it.

"Once the reefs have died, you'll see these (fish) hanging around for a while getting thinner and thinner and then you'll start losing a lot of coral associated fish," he said.

In this way, Dr Ridgway said coral was like a canary in a coal mine.

Great Barrier Reef Marine Park Authority reef recovery director David Wachenfeld said the reef had seen temperatures 1-2 degrees above average over the past week.

"It was like that all the way through February," he said.

"In fact, a lot of February was worse and it's been that way all the way through March.

"So we've had two solid months of heat stress accumulating."

It wasn't all doom and gloom however, with all three speakers saying they believe there's still time to save the reef.

"There are two things we can do," Mr Wachenfeld said.

"We've got to reduce the rate and magnitude of climate change and we've got to do it urgently.

"The other thing that we can do is actually build the local resilience of the reef.

"That's about protecting biodiversity, improving water quality, making sure our fishing is sustainable and making sure we don't overdevelop the coastline."

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