Coral Bleaching: Reefs Adapted To Warm Waters Are Just As Threatened By Climate Change

Being used to warm waters may not be enough for corals surrounding Australia's Kimberly region, according to researchers from the ARC Centre of Excellence in Coral Reef Studies. A recent study revealed corals in north Western Australia are just as susceptible to heat stress and bleaching as their counterparts living in less extreme environments. 

"We found that exceeding their maximum monthly summer temperatures by one degree Centigrade for only a few days is enough to induce coral bleaching," Dr. Verena Schoepf, one of the study researchers from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at the University of Western Australia's Oceans Institute, explained in a news release. "We were surprised because under normal conditions, Kimberley corals can tolerate short-term temperature extremes and regular exposure to air without obvious signs of stress."

Coral bleaching results from a loss of algae living within the coral's tissues, which ultimately provides them with energy and give them their natural colors. Corals and algae depend on each other to survive, but as oceans warm the algae leaves. This exposes the corals and makes them more vulnerable to bleaching.  

The Kimberly region is home to some of the largest tropical tides in the world. Inevitably, this creates naturally extreme and dynamic coastlines, along which corals from typical reefs could never survive.  

"Unfortunately the fact that Kimberley corals are not immune to bleaching suggests that corals living in naturally extreme temperature environments are just as threatened by climate change as corals elsewhere," Dr. Schoepf added.

Based on the recent study, researchers concluded both branching and massive corals exposed at low tide coped better with heat stress compared to corals from deeper water. Additionally, massive corals have a better chance of surviving and recovering from a bleaching event than branching corals.

"However this doesn't mean that they are immune to bleaching," Professor Malcolm McCulloch, co-author from the Coral CoE, said.  

Their findings, recently published in the journal Scientific Reports, suggest current rates of ocean warming could put corals at a higher risk of severe bleaching than previously thought. Based on recent weather predictions, the Kimberly region could be significantly impacted by 2016.

"With the third global bleaching event underway, it has never been more urgent to understand the limits of coral thermal tolerance in corals," Professor McCulloch concluded.  

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