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The Guardian
2 days ago
- Science
- The Guardian
‘It was our hope spot': scientists heartbroken as pristine coral gardens hit by Western Australia's worst bleaching event
The Rowley Shoals are on many a diver's bucket list. The three coral atolls, hundreds of kilometres off the Western Australian coastline, are teeming with pristine coral gardens that for a long time, unlike many of the world's reefs, had escaped the ravages of global heating. 'I've seen a fair bit of death and destruction, but Rowley Shoals was always the place that was still standing,' says Dr James Gilmour, a research scientist at the Australian Institute of Marine Science. 'Just the sheer abundance of life is incredible. It was our hope spot. It's the reef I love more than any other. So this was super emotional.' Starting in August 2024, an unprecedented heatwave has swept across Western Australia's reefs, turning corals white from the World Heritage-listed Ningaloo all the way to Ashmore Reef, about 1,500km north-east. Now, teams of government scientists are reporting widespread coral death, which they say is the worst bleaching to hit the state. There are still areas of live coral, and some bleached coral will recover, but as scientists gather data, the scale of mortality has left many shocked. At Rowley Shoals, Gilmour, who has been researching corals for 30 years, says a visit in mid-April presented a devastating and confronting scene. 'It was several weeks after the peak heat stress. Some corals were still bleached white, but most had died. We saw that over vast areas,' he says. 'The structure is still there but they're now all covered in algae. Everywhere was dead coral skeletons.' Coral bleaching describes a process whereby the coral animal expels the algae that live in its tissues and give it its colour and much of its nutrients. Without its algae, a coral's white skeleton can be seen through its translucent flesh, giving off a bleached appearance. Mass coral bleaching over large areas, first noticed in the 1980s around the Caribbean, is caused by rising ocean temperatures. Some corals also display fluorescent colours under stress when they release a pigment that filters light. Sunlight also plays a role in triggering bleaching. Corals can survive bleaching if temperatures are not too extreme or prolonged. But extreme marine heatwaves can kill corals outright. Coral bleaching can also have sub-lethal effects, including increased susceptibility to disease and reduced rates of growth and reproduction. Scientists say the gaps between bleaching events are becoming too short to allow reefs to recover. Coral reefs are considered one of the planet's ecosystems most at risk from global heating. Reefs support fisheries that feed hundreds of millions of people, as well as supporting major tourism industries. The world's biggest coral reef system – Australia's Great Barrier Reef – has suffered seven mass bleaching events since 1998, of which five were in the past decade. The sandy-bottomed reef lagoons – usually alive with colourful branching corals and fish filling every space – are now 'huge fields of staghorns, all dead,' Gilmour says. 'The outer slope drops from a few metres to 50 metres and it's like looking down the side of a cliff. You can usually see the life down there – the sharks swimming. But this time we looked down the side of the mountain and you didn't see life.' Gilmour says the temperatures at every reef north of Ningaloo reached as high as or higher than ever recorded. 'We've never had every major WA reef affected in a single event. This is the worst coral bleaching event recorded for WA reefs.' Dr Chris Fulton, a principal research scientist at AIMS, has been going to the World Heritage-listed tourism hotspot of Ningaloo since 2008. After a research visit in late January when corals were turning white, he and colleagues returned last week. 'It was a real shock and a lot of us were deeply affected,' Fulton says. 'You have the desert going right to the water's edge and you can just step off the shore in to a spectacular reef that you don't get anywhere else. These natural features are comforting. So imagine if they've all been painted white. Every shape and size of coral colony are being affected with bleaching and mortality.' Fulton spends hundreds of hours a year diving and, usually, the water temperature isn't something that registers. 'But we were all struck by the massive heat in the lagoon,' he says. Ningaloo has bleached badly before, in 2010/11, but Fulton says this year is worse. Temperature loggers in the water showed it was up to 3C above normal – levels that can be devastating for corals. Sign up for Guardian Australia's breaking news email After surveying one personal favourite spot, known as the Oyster Stacks, Fulton says he emerged 'bawling my eyes out'. 'I couldn't believe how bad it was – but then there's a resolve to document what's happening.' Fulton says the seaweed meadows used by fish as nurseries have fared OK, but the fish that feed on coral – such as the Chevron butterfly fish – are crowding around the few surviving corals. 'They're often the pretty fish, but they're usually the first to go. They literally starve to death, and we're starting to see that already. I'm not optimistic they're going to survive.' One bright spot, says Fulton, is that some individual corals across a wide variety of types had managed to survive when others of the same species had died. 'I'm astounded by that,' he said. 'So it's a genuine source of optimism.' Elsewhere along the WA coastline, the story of coral death is repeated. At the Kimberley Marine Research Station, intern and recent university ecology graduate Tara Thomsen, from Melbourne, says even though temperatures have started to fall, there is still bleaching 'I've found it pretty heartbreaking, coming to this beautiful part of the world with pristine areas but seeing in some places the reefs reduced to rubble. It's pretty sad,' she says. Phillip 'Bibido' McCarthy, coordinator of Bardi Jawi Rangers, says there are 50 or 60 small islands off the Dampier Peninsula, many with big reefs. 'We've had a big impact right through the coastline,' McCarthy says. 'We can see the whiteness even off the boat ramp. It's quite terrible. Our resources come from the ocean. These habitats are where the fish grow. I'm 56 but I've never seen anything like this.' Dr Thomas Holmes coordinates the marine science program at the WA government's Department of Biodiversity, Conservation and Attractions. Reefs have been monitored from the air and in the water. He says the heatwave started to reach levels to bleach corals in December. At Ningaloo, bleaching is still unfolding. 'I'm not afraid to use the word unprecedented,' he says. 'We have never seen this in recorded history, whether it's the period of time – it started getting hot in December and some places are still bleaching – or in how hot it's got. And it's unprecedented in scale.' Dr Claire Spillman, principal research scientist at the Bureau of Meteorology, confirms marine heatwave conditions started in WA as early as August 2024 and are ongoing in central and southern parts of the state's waters. Australia's ocean areas have warmed on average by 1C since 1900, and several WA ocean areas have seen their hottest months in this latest heatwave. 'Warming events like the one we are seeing now off the WA coast are becoming more frequent,' Spillman says. Helping fuel the heat, too, has been an accumulation of warmer water in the far western Pacific, which pushed down the WA coast to become part of the Leeuwin current running south. About 90% of the extra heat trapped by rising levels of greenhouse gases has been absorbed by the ocean. Gilmour says the sheer scale of ocean heating is something corals in the region have never had to deal with. 'When you're out there it looks like everything is dead, and it's overwhelming. For Rowley Shoals it will take 10 years [for some recovery] – if we don't get another severe bleaching event. But of course, we are going to get one. 'What really worries me and others is not so much the loss of the corals and reefs, it's that we have reached the point where all these ecosystems are in the same situation. 'And what does this mean? 'This is what 1.5C above the preindustrial [average temperature] means. Things will get a lot worse before it gets better, and that's what makes me sad.'
Perth Now
4 days ago
- Health
- Perth Now
Underwater robot makes grim discovery off Fremantle coast
An underwater robot drone has exposed the extent of a coral reef crisis right on North Fremantle's doorstep. A high-tech robot named Hydrus was deployed last month to capture photos and videos at Hall Bank Reef, which is just off the coast of Port Beach in North Fremantle. But when Dr Alec McGregor went back to the office to stitch together the footage, the 3D digital render painted a dire picture of a barren seabed with lifeless corals. Your local paper, whenever you want it. 'Basically, what we saw was a dramatic reduction in coral cover of the area that we scanned,' he said. The imagery showed severe coral bleaching and fragmentation, which Dr McGregor said laid bare a hidden yet escalating crisis at one of the world's southernmost reefs. Dr McGregor is the senior AI engineer at Advanced Navigation, the company behind the underwater robot launched in 2022. Hydrus — otherwise called an autonomous underwater vehicle (AUV) — is a small 7kg robot that captures geo-referenced high-resolution imagery and 4K video in parallel. An underwater drone has exposed a serious coral reef crisis right on North Fremantle's doorstep. Credit: Advanced Navigation The footage is then sewn together to create a 3D model of the coral reefs below, which can help provide real examples of current coral bleaching to marine scientists. 'Being able to scan coral reefs every six months, it allows us to get an actual idea of how fast these coral reefs are degrading, and gives those experts the data to make better decisions about how to combat bleaching,' Dr McGregor said. Last month's mission was in collaboration with marine consultancy O2 Marine, which Dr McGregor considered a typical example of the rising number of companies which hire Hydrus. 'There's been a huge uptake in the interest in the marine space,' he said. Dr McGregor is the senior AI engineer at Advanced Navigation, the company behind the underwater robot launched in 2022. Credit: Advanced Navigation 'We have many different customers all over the world and here in Australia that are using the robot for various different application. 'Some customers include the Australian Institute of Marine Science who have been looking at coral reefs up in Ningaloo and at the Great Barrier Reef. 'We also do work in the US for the National Oceanographic and Atmospheric Association ... so people are definitely catching on.' Dr McGregor said findings of a coral-bleached reef at Halls Bank highlighted the growing climate crisis on WA's doorstep. 'It's important that our State Government knows that coral bleaching is actually taking place, that this is not just happening on the Great Barrier Reef but it's also happening in WA,' he said. 'I think that that's something that the government and people in charge should know, and they'll be able to make more informed decisions and data-driven decisions based on that.'
7NEWS
06-05-2025
- Science
- 7NEWS
Reef-saving critter sparks hope for Great Barrier Reef
Tiny crabs are turning the tide on one of the Reef's deadliest threats — devouring baby crown-of-thorns starfish at a rate that has stunned scientists. The crown-of-thorns starfish (COTS), infamous for its appetite for live coral, has long been blamed as a key culprit in the decline of Australia's iconic Great Barrier Reef, Queensland. They are a 'major contributor' to coral loss as they extend and wrap their stomachs around the coral to digest their tissues. Currently, management of COTS outbreaks relies on teams of divers to hand-pick starfish off the reef, which is time consuming and labour intensive. But a surprising new ally for our reefs has emerged from the shadows of the seafloor: Tiny decapod crabs. Researchers from the University of Queensland (UQ) and Australian Institute of Marine Science (AIMS) made the discovery through a controlled lab study. 'Our research detected over 30 new species that consume COTS during their vulnerable juvenile life stage,' said Dr Kennedy Wolfe, the study's lead author from the UQ. 'The decorator crab was a particularly voracious feeder, demonstrating the highest known rate of predation on COTS.' These findings are consistent in the wild with detected starfish DNA inside the stomach of seven species of crabs collected from reefs. Wolfe said that the results were promising and 'crucial to our ability to manage COTS outbreaks and their impacts to coral reefs. 'The smaller critters often do a lot more than we give them credit for, just like the bees and the earthworms on land.' It's a numbers game Researchers believe these tiny critters consume more than five baby starfish per day, which is a significantly higher rate than predators like the starry pufferfish and giant triton snails that only eat one adult starfish every few days or week. 'By better understanding these ecological connections, scientists are opening new possibilities for more natural, scalable approaches to reef conservation,' The Great Barrier Reef Foundation said. 'What we now need to determine is whether these crabs are depleted on some reefs, and why,' Wolfe added. 'If they are impacted and depleted, the causes would need to be managed to ensure these crabs have the best fighting chance to perform their role in consuming COTS.' He said the crabs could potentially be used as a biocontrol option on reefs heavily affected by COTS, but emphasised that introducing populations would need careful research to prevent unintended ecological impacts.
Yahoo
23-04-2025
- Science
- Yahoo
Largest coral bleaching event on record impacts 84% of world's reefs: NOAA
The world's coral reefs are in the midst of the fourth and largest global bleaching event in recorded history, the National Oceanic and Atmospheric Administration announced this week. The grim milestone was recorded between January 2023 and April 2025, with the agency documenting that bleaching-level heat stress has impacted 83.7% of the world's coral reef area. The impacted reefs span at least 83 countries and territories, the agency said. MORE: 4th global coral reef bleaching event underway as oceans continue to warm: NOAA Since early 2023, mass bleaching of coral reefs has been confirmed in the Atlantic, Pacific and Indian ocean basins, including parts of Florida and the coastline of the United States, the Caribbean, Central America, South America, Australia, the South Pacific, the Persian Gulf, coasts of East Africa and Indonesia, according to NOAA. The agency deemed this ongoing bleaching event "the biggest to date," noting that the previous record was set with 68.2% of reefs affected during the third-largest bleaching period, between 2014 and 2017. The first and second global coral bleaching events occurred in 1998 and 2010, respectively, according to the agency. MORE: Thermoresistant 'super corals' offer hope amid climate change: Scientists Bleaching occurs when warmer ocean temperatures cause the expulsion of algae that live in the coral tissue. This leaves the coral completely white, known as coral bleaching. Coral bleaching does not necessarily mean corals will die, according to NOAA, which noted that corals can recuperate if the strain on their ecosystems is reduced. At a local level, storms, disease, sediments and changes in salinity can cause corals to bleach; however, mass bleaching, when several varieties of coral reefs are bleached, is largely caused by increased sea temperatures, according to the Australian Institute of Marine Science. Largest coral bleaching event on record impacts 84% of world's reefs: NOAA originally appeared on
Yahoo
23-04-2025
- Science
- Yahoo
Largest coral bleaching event on record impacts 84% of world's reefs: NOAA
The world's coral reefs are in the midst of the fourth and largest global bleaching event in recorded history, the National Oceanic and Atmospheric Administration announced this week. The grim milestone was recorded between January 2023 and April 2025, with the agency documenting that bleaching-level heat stress has impacted 83.7% of the world's coral reef area. The impacted reefs span at least 83 countries and territories, the agency said. MORE: 4th global coral reef bleaching event underway as oceans continue to warm: NOAA Since early 2023, mass bleaching of coral reefs has been confirmed in the Atlantic, Pacific and Indian ocean basins, including parts of Florida and the coastline of the United States, the Caribbean, Central America, South America, Australia, the South Pacific, the Persian Gulf, coasts of East Africa and Indonesia, according to NOAA. The agency deemed this ongoing bleaching event "the biggest to date," noting that the previous record was set with 68.2% of reefs affected during the third-largest bleaching period, between 2014 and 2017. The first and second global coral bleaching events occurred in 1998 and 2010, respectively, according to the agency. MORE: Thermoresistant 'super corals' offer hope amid climate change: Scientists Bleaching occurs when warmer ocean temperatures cause the expulsion of algae that live in the coral tissue. This leaves the coral completely white, known as coral bleaching. Coral bleaching does not necessarily mean corals will die, according to NOAA, which noted that corals can recuperate if the strain on their ecosystems is reduced. At a local level, storms, disease, sediments and changes in salinity can cause corals to bleach; however, mass bleaching, when several varieties of coral reefs are bleached, is largely caused by increased sea temperatures, according to the Australian Institute of Marine Science. Largest coral bleaching event on record impacts 84% of world's reefs: NOAA originally appeared on
