Australia’s Great Barrier Reef is hit with mass bleaching but another coral reef flourishes in Cambodia

Live corals in many colours mainly pink and red.
Live Corals by Qui Nguyen on Unsplash
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Coral reefs are vibrant rocky formations found in shallow coastal regions, each representing a community of living organisms. Australia’s Great Barrier Reef is a UNESCO World Heritage Site and the world’s largest coral reef system. It  spans an impressive 133,000 square miles (345,000 square kilometers), hosting over 1,500 fish species and 411 varieties of hard corals. This magnificent ecosystem not only enriches the Australian economy with billions of dollars annually but also serves as a premier attraction for international visitors, celebrated as one of Australia’s and the world’s most extraordinary natural marvels. 

Like other parts of the world, it is also being impacted by climate change and has been facing severe coral bleaching events due to global heating. The most recent mass bleaching event in 2024 marks the fifth occurrence in just eight years, with extensive coral bleaching observed across the southern section of the reef. The reef’s managers confirmed the mass bleaching in early March 2024, due to the rising ocean temperatures caused by the global climate crisis and amplified by El Niño. 

Coral bleaching occurs when high temperatures force the corals to expel symbiotic algae and turn white, making them susceptible to, starvation, disease and death. Coral reefs support commercial fisheries and protect coastlines from storms. However, according to one study they have declined by half since the 1950s, mainly due to climate change.

Aerial and in-water surveys on more than 300 inshore, mid-shelf and offshore reefs have revealed widespread bleaching, raising concerns about the health of this vital ecosystem. The southern section has experienced significant coral mortality, with corals hundreds of years old severely affected. Scientists suspect that a seventh mass bleaching event may be underway, highlighting the ongoing threat posed by climate change to this biodiversity hotspot. The impact of these bleaching events on the Great Barrier Reef is alarming, with mass coral mortality also reported in the northern and central sections. The scientists found “prevalent shallow water coral bleaching” on most reefs surveyed. In a recent study, researchers confirmed that 35% of corals in these regions have perished due to mass bleaching caused by unusually warm waters.

The frequency of these bleaching events is increasing, leaving the reefs with limited time to recover as global temperatures rise. There are similar reports from coral reefs around the world during the past 12 months, the reef’s managers said.

Similar high level mass bleaching at the Great Barrier Reef have previously been observed in 1998, 2002, 2016, 2017, 2020 and 2022. The one in 2022 is of particular concern because it occured during the global La Niña event, which has a cooling effect, as opposed to El Niño’s warming effect.

“Climate change is the biggest risk not just to the Great Barrier Reef in Australia but also to coral reefs around the world,” said Australia’s Environment Minister Tanya Plibersek in a video statement. “We know that we need to give our beautiful reef the best chance of survival for the planet and animals that call it home, for the 64,000 people whose livelihoods depend on reef tourism.”

“It’s devastating,” said AMCS Great Barrier Reef campaign manager Dr. Lissa Schindler. “This is a huge wake-up call for Australia and the global community that we need to do much more to address climate change, which is driving the marine heatwaves that lead to coral bleaching.”

There is some good new however. In contrast to the challenges faced by the Great Barrier Reef, there is a beacon of hope in Cambodia’s coral reefs. Despite global trends of coral decline, Cambodian reefs are flourishing with new life and resilience to warming waters. Researchers have observed a remarkable spawning event off the coast of Cambodia, where different coral colonies released bundles of eggs and sperm into the ocean, initiating the reproduction process for new corals.

This spawning event offers hope for these ecosystems under threat due to global warming, showcasing their ability to produce new generations of corals even amidst environmental stressors like overfishing and marine heatwaves.

In tropical waters globally, substantial portions of coral reefs begin releasing numerous small pearl-sized spheres. These spheres come in various colors like pink, red, orange, or yellow. Briefly, the ocean transforms into a mesmerizing snow globe before these spheres drift away.This natural occurrence, termed spawning, is the primary method through which many corals procreate. Each sphere comprises a mix of eggs and sperm from an individual coral colony. Remarkably, distinct colonies of the same species somehow synchronize their spawning to occur simultaneously, ensuring that their reproductive materials can unite to generate new coral offspring.

“It was like it was snowing,” Tharamony Ngoun, a marine species and ecosystems officer at Fauna & Flora, who observed the spawn, told Vox. “It was so amazing.”

Here is the video of the event:

The reefs in Cambodia and in the broader East Asian region appear to be bucking the global trend of decline. Surveys indicate that they haven’t declined in recent decades, perhaps because they’re more resilient to warming. Their secret to survival may ultimately help safeguard ailing reefs elsewhere.

“The coral is thriving,” said Matt Glue, a marine technical specialist at Fauna & Flora, which sent a team earlier this month to try to observe spawning. “Everywhere we would go we would see more colonies that were spawning. It’s very hopeful.”

Elsewhere however the tragic story continues, with the IPCC (lead scientific authority on climate change) saying that if the world warms by 1.5 degrees Celsius, relative to pre-industrial times, coral reefs could decline by 70 percent to 90 percent.

The contrasting narratives of coral bleaching in the Great Barrier Reef and the thriving coral reefs in Cambodia underscore the urgent need for global action to address climate change and protect marine ecosystems. While one region grapples with repeated bleaching events and coral mortality, another demonstrates resilience and potential for recovery. These stories emphasize the critical importance of conservation efforts and sustainable practices to safeguard our oceans’ biodiversity for future generations.

I am a Chartered Environmentalist from the Royal Society for the Environment, UK and co-owner of DoLocal Digital Marketing Agency Ltd, with a Master of Environmental Management from Yale University, an MBA in Finance, and a Bachelor of Science in Physics and Mathematics. I am passionate about science, history and environment and love to create content on these topics.

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