Aerial surveys of more than 500 coral reefs from Cairns to Papua New Guinea reveal that the most pristine section of the Great Barrier Reef is currently experiencing the worst, mass bleaching event in its history, with the overwhelming majority of reefs being ranked in the most severe bleaching category.
“This has been the saddest research trip of my life,” says Prof. Terry Hughes, convenor of the National Coral Bleaching Taskforce. “Almost without exception, every reef we flew across showed consistently high levels of bleaching, from the reef slope right up onto the top of the reef. We flew for 4000km in the most pristine parts of the Great Barrier Reef and saw only four reefs that had no bleaching. The severity is much greater than in earlier bleaching events in 2002 or 1998.”
At this time, it is how much, if any of the coral can or will survive the bleaching, but it does place additional stress on the coral, and makes the coral Bleaching events have occurred before, although this one looks exceptionally severe. According to NOAA “In 2005, the U.S. lost half of its coral reefs in the Caribbean in one year due to a massive bleaching event”
Bleaching is caused by stresses on the coral including changes in temperature, light, or a change in nutrients. The stress causes the choral to expel the colorful algae (zooxanthellae) living inside them.
The first thing to understand is that corals get their brilliant colors from tiny algae that live in their tissues. These tiny organisms live in harmony with coral animals, and they basically share resources,” Wear explains. “For example, the most important thing that the algae do is provide food to the corals through carbohydrates they produce during photosynthesis.”
“The next thing to understand is that corals have a limited temperature range within which they can live,” Wear continues. “When it gets too hot, they get stressed out—and this relationship with the algae goes sour. The tiny algae are ejected from the corals, turning them white, thus the term ‘bleached.’”
And what happens then? “If these algae aren’t reabsorbed in the near term, the coral will die,” says Wear. “They just can’t survive long-term without them.”
In addition to their beauty, coral reefs are home to 25% of all marine species. If we lose the reefs, all those species would lose their habitats