The Great Barrier Reef (GBR) is one of the ecosystems most severely impacted by global warming. The world’s largest coral reef system has been lashed with six mass bleaching events, killing the corals. A recent study has discovered that a part of the GBR has been hit by the most widespread and previously unseen bleaching episode around the One Tree Island reef in 2024.
For the study, scientists documented 462 colonies of corals at One Tree Island in the southern GBR after the heat stress began in early 2024. The heat stress turned the corals white, damage which was further exacerbated by flesh-eating disease. This widespread coral bleaching outbreak killed over 40 percent of individual corals around the island.
Image: Sydney University
Published in the Association for the Sciences of Limnology and Oceanography (ASLO), the study discovered that only 92 coral colonies were safe from bleaching. By the time the analysis for the study ended in July 2024, 193 colonies were dead and 113 were still affected by the bleaching.
Marine biologist Prof Maria Byrne from the University of Sydney and lead author of the study, said, “Seeing those really massive colonies die was really devastating. I have gone from being really sad to being really cranky. We have been trying to get the message across about climate change for ages.”
The Australian Institute of Marine Science surveyed eight reefs in the Capricorn-Bunker sector of the reef. It discovered that live hard coral cover significantly decreased on seven reefs due to 2024 mass bleaching, storm swell, and coral disease. This contributed to the single largest annual decline in hard coral cover since the survey began in the mid-1980s, with a relative 41 percent depletion over the years.
Byrne and her fellow researchers used temperature loggers, and video and direct observations to document the welfare of 12 different types of coral. According to Byrne, this was the worst bleaching recorded at One Tree Island reef. She said the corals that were still white at the end of their research could either recover or die.
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Richard Leck, the head of oceans at WWF-Australia, said, “We are yet to see the full data about last summer’s coral bleaching, but it’s clear there has been major mortality in areas from the north and this new research shows major mortality in the south. The reef is under more heat stress this summer, especially in the north, and there’s a risk we could see another back-to-back bleaching event. It’s a case of Russian roulette whether that occurs or not. We know the reef is under increasing pressure from climate change and its world heritage status is under increasing pressure.”
The current state of the GBR and the upward trajectory of climate change could be devastating for the ecosystem. Only time will tell which way the tide turns for the reefs in the GBR.
Via: The Guardian