It’s getting harder for corals to beat the heat.
A new study examined how corals can survive bleaching — a process that occurs when the algae that live within their tissue are expelled, turning the usually colorful corals a ghostly white.
High water temperatures are among the factors that can trigger bleaching. If waters cool soon enough after warming, the algae return. But extended heating causes the corals to die.
The team of researchers found that when surges in temperature occurred rapidly, this resulted in coral bleaching.
But when corals were slowly exposed to temperature increases and allowed to cool briefly before heating up even more, they were able to avoid being damaged by a heat wave. This two-step heating process actually helped the corals adapt their physiology, the researchers found.
"I like the runner analogy. For those that can do a practice run first and do a little bit of training, they can handle it," explained Tracy Ainsworth, lead author and ARC Centre of Excellence for Coral Reef Studies researcher.
Australia’s Great Barrier Reef is currently being devastated by its worst bleaching event in recent history, with about 75 percent of its northern half currently devoid of algae. On top of that, climate models predict sea temperatures will rise 2 degrees by the end of this century — heating to this extent could completely overwhelm the reef.
The researchers’ computer simulations predict that protective temperature pulses — those that allow the corals to prepare for further heating — will cease once the water temperature increases by 0.5 degrees. Considering current warming trends, this could occur as early as 2050.
“If that protective mechanism does get lost going into the future, then what we’ve seen so far as being bad impacts could become worse,” says study coauthor Scott Heron, a physical oceanographer with the National Oceanic and Atmospheric Administration’s Coral Reef Watch.
But their models also indicate that immediate emissions reductions would greatly improve the odds of survival for much of the Great Barrier Reef.
For the time being, it appears that the fate of this natural wonder is still in our hands.