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Researchers have confirmed that the Great Barrier Reef of Australia has experienced its third coral bleaching event in five years.
A bleaching event is when the coral expels a type of algae that provides up to 90 percent of its energy. This expulsion can occur when the coral is under stress from heat stress, also known as when the ocean temperature rises beyond healthy levels.
What’s more concerning is how these events are spreading across the Great Barrier Reef.
Professor Terry Hughes, director of the ARC Center of Excellence for Coral Reef Studies at James Cook University, said: “We examined 1,036 reefs from the air over the past two weeks in March, to measure the extent and severity of bleaching of corals throughout the barrier reef region.
“For the first time, severe bleaching has affected all three regions of the Great Barrier Reef: the north, the center, and now much of the southern sectors.”
It doesn’t look good for the Reef. In February, researchers stated that the area recorded its highest monthly sea surface temperatures since records began in 1900.
They are concerned about how much impact it will have in the coming months and whether the coral reefs will be able to cope.
Professor Morgan Pratchett, also from Coral CoE at JCU, led ongoing studies to assess how bad this recent bleaching event has been.
He said: “A pale or slightly bleached coral generally regains its color in a few weeks or months and survives.
“We will return underwater later this year to assess the coral losses from this most recent event.
“The north was the worst affected region in 2016, followed by the central region in 2017. In 2020, the cumulative bleaching footprint has expanded further to include the south.”
Experts have also noted that the time period between these bleaching events is shortening, which means that the coral reef has less time to fully recover.
Professor Hughes says that the number of reefs that have prevented bleaching is shrinking each year.
“As the summers get hotter and hotter, we no longer need an El Niño event to trigger massive bleaching on the Great Barrier Reef scale,” said Professor Hughes.
“Of the five events we have seen so far, only 1998 and 2016 occurred during El Niño conditions.
“We have already seen the first example of consecutive fading in the consecutive summers of 2016 and 2017.”
