The massive coral bleaching event that has hit the Great Barrier Reef will get even worse if current climate events continue, according to a new study by scientists from the Australian Research Council Centre of Excellence for Coral Reef Studies.
The team revealed that although corals possess a mechanism that prepares them for bleaching events, climate change is at risk of destroying the temperature patterns that allow them to utilize this mechanism.
"Coral is an animal that has a plant living inside its cells," said Tracy Ainsworth, who led the team.
This plant is algae, which gives it its unique color and provides it with nutrition. However, when water temperatures rise, the coral expels the algae, revealing its white skeleton and typically ending in death.
Despite the dangers of higher temperatures, corals can protect themselves due to the predictable temperature patterns that precede bleaching events: water gets hot, but not hot enough to cause bleaching, before falling for 10 days and then rising again to temperatures that can cause bleaching. This pattern allows corals to implement protective measures by following it.
The team examined 27 years of coral reef records for the Great Barrier Reef and looked for times when the local temperatures became extreme enough to cause bleaching, which they refer to as "thermal stress events."
The results show that 75 percent of these events possessed the temperature pattern that allows the corals to protect themselves. However, in 20 percent of the events, the temperatures rose steadily, leaving the corals little time to prepare for the bleaching. Corals experienced two temperature peaks that caused bleaching in five percent of these cases.
The team then looked to the future in order to determine how climate change will affect this process.
"Our hope was that [the protective pattern] would increase into the future," said Scott Heron of the NOAA, co-author of the study. "However, our study showed that the proportion of events with that protection mechanism is actually modeled to decrease."
The study revealed that if global warming continues and sea surface temperatures rise by 3.6 degrees Fahrenheit by 2100, just 22 percent of the bleaching events will fall within the protective pattern, spelling doom for the Great Barrier Reef.
"I think we shouldn't lose hope, though," Ainsworth said, suggesting that the reefs that do experience the protective temperature patterns should be the focus of special protective measures and could help restore the health of the reef.
The findings will be published in the April 15 issue of the journal Science.
