The Great Barrier Reef has suffered extensive damage to the reef system over the last half decade due to warming ocean temperatures causing mass bleaching events and that trend continues to occur. According to the Australian Government, who utilized aerial photos due make their findings, the GBR has just gone through its third mass bleaching in the last five years.
The aerial work was performed by the Australian Government Great Barrier Reef Marine Park Authority in collaboration with the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University.
While cooler weather of late has swept through the region, the heat though the summer months, in particular February, led to bleaching which is now evident in the aerials.
In particular, the researchers observed:
- The worst bleaching is on reefs that suffered the highest heat stress this summer, which extended across large areas of the Reef.
- A wide range of bleaching occurred, ranging from no bleaching to the most severe category. Some southern areas of the Reef that had little or no bleaching in 2016 and 2017 have now experienced moderate or severe bleaching.
- Key tourism reefs in the Northern and Central areas of the Reef experienced only moderate bleaching, from which most corals should recover.
- Moderate and severe bleaching occurred on coastal and mid-shelf reefs in the far north where the corals remaining after the 2016 and 2017 events are relatively heat-tolerant.
- They also identified pockets of the Reef that remain unaffected with healthy areas of reefs.
The areas that saw the highest heat stress saw up to 80% of coral bleaching occur here.
Coral bleaching occurs when coral polyps expel the algae that live inside their tissues due a stress related event such as temperature changes. The coral polyps live in an endosymbiotic relationship with these algae, which are crucial for the health of the coral and the reef. The algae provides up to 90 percent of the coral’s energy. When the algae is expelled the, bleached corals continue to live but begin to starve after bleaching and while some corals may recover, some in the GBR have not been able to due to the drastic change occurring.
While the news is certainly troubling as it is expected that waters continue to warm across the planet, unless drastic and immediate action is taken on climate change, there is good news in that there are pockets of the reef that remain unaffected.
In a weekly update on the reef health, Dr David Wachenfeld echoed that sentiment-
“It is important to remember bleached corals are not dead corals — on mildly or moderately bleached reefs there is a good chance most bleached corals will recover and survive this event,” writes the agency. “Equally, on severely bleached reefs, there will be higher mortality of corals.”
The teams of researchers will continue to asses the damage and potential long term impact of the bleaching event through the coming weeks.
“With aerial surveys being completed this week, we will better understand the extent and severity of this bleaching event. Further analysis will continue over the coming weeks,” writes the marine park authority in a statement.
With bleaching events inevitable at this point, coral researchers will be doing their best to identify how to mitigate and help the reef survive through the drastic change.