Scientists and reef lovers alike are in alarm over the recent news that has come from the aerial surveys conducted by the ARC Centre of Excellence for Coral Reef Studies in Queensland, Australia. For the second year in a row, surveys show severe coral bleaching in the Great Barrier Reef off the coast of Australia, and scientists fear that this might be a point of no-return for the planet’s largest reef system.
The surveys reported bleaching at 800 individual coral reefs across 8,000km. Such extreme mass bleaching has only been seen once before: last year. While other mass bleaching events have happened twice before other than last year (in 1998 and 2002), this is the first time it has ever happened back to back years. Such an unprecedented event leaves scientists questioning if the corals will be able to survive.
“The significance of bleaching this year is that it’s back to back, so there’s been zero time for recovery,” Professor Terry Hughes, who led the surveys, told the Guardian. Typically, it takes at least a decade or more for corals to reach a full recovery. “It’s too early yet to tell what the full death toll will be from this year’s bleaching, but clearly it will extend 500km south of last year’s bleaching.”
While 2016’s mass bleaching covered the northern third of the reef, the event this year is the worst in the middle section of the reef. Unfortunately, parts of those areas overlap, which means that some of the reefs have gotten a double whammy of severe bleaching.
What exactly is bleaching? Bleaching happens when coral is exposed to higher than normal water temperatures (cough cough, climate change). Higher temperatures "cause corals to expel tiny photosynthetic algae, called 'zooxanthellae,' " the ARC Centre said. "The loss of these colorful algae causes the corals to turn white, and bleach.” This makes the animals extremely fragile, with higher chance of breaking.
Although corals are able to recover if the ocean temperatures go back to favorable conditions, prolonged stress (such as that experienced by multiple bleachings) may kill the corals. Following a study in Nature, local measures in Australia may not be able to protect the reefs from bleaching. In order to really protect corals, the reef "ultimately requires urgent and rapid action to reduce global warming."
While many have lost hope, some scientists continue to dedicate their lives to coming up with conservation strategies for coral reefs. One of these strategies is the field of coral restoration, in which marine biologists not only physically grow and replenish bleached and dead corals, but also investigate which coral species are the most adaptable to warmer and more acidic waters.