The Great Barrier Reef close to the seventh mass bleaching phenomenon: what it means

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The Great Barrier Reef close to the seventh mass bleaching phenomenon: what it means

Climate changes

Due to anomalous sea temperatures, several areas of the Great Barrier Reef in Australia are experiencing bleaching. What it means and why corals risk dying due to the climate crisis.

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Australia 's Great Barrier Reef , one of the most biodiverse ecosystems in the world, could be hit by the seventh major mass bleaching event due to the ongoing climate crisis . Recent helicopter reconnaissance conducted by experts from the Great Barrier Reef Marine Park Authority have in fact detected significant bleaching, especially in the southern area, where 27 coastal and 21 offshore barriers (Keppel Group and Capricorn-Bunker Group) show signs of the phenomenon. But there are reports along more than 1,000 kilometers of the enormous natural structure stretching off the Queensland coast. The risk, as indicated, is that the seventh mass event is underway after those that occurred in 1998, 2002, 2016, 2017, 2020 and 2022.

But what exactly is coral bleaching ? This is a phenomenon that occurs when the average temperature of sea water exceeds that at which these animals are used to living by about 2°C , which live in symbiosis with unicellular algae called zooxanthellae . These organisms are not only responsible for the beautiful colors of the coral reef, but also provide valuable nutrients to corals through photosynthesis. When the anomalous heat lasts for weeks the corals are forced to expel algae , bleaching as a result. Some coral species fluoresce. If the temperature returns to normal values, the algae quickly return and the corals can feed again, but if the thermal stress lasts too long they can literally starve, transforming the reefs into vast expanses of white skeletons.

Observations with helicopters and small aircraft are essential to understand the extent of the bleaching phenomena; after the helicopter reconnaissance conducted in recent days, Australian scientists will fly over the Great Barrier Reef – which extends for 2,300 kilometers – in its entirety with small planes and will also conduct underwater expeditions, to understand the actual extent and severity of the phenomenon . The data will confirm or not the seventh episode of mass bleaching. As indicated by the Guardian, according to Richard Leck of WWF Australia the coral reef is on the brink of this event, while for the Australian Marine Conservation Society we will have to wait for the next few weeks to actually understand how things are. What is certain is that the Great Barrier Reef risks becoming extinct by the end of the century, because these repeated waves of anomalous heat break down its resilience , preventing the corals from recovering.

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The latest findings from the Reef Authority indicate that thermal stress continues to accumulate and that throughout the Marine Park and the sea surface temperature is 0-2 °C higher than average, therefore falling within the risk range. “The highest anomalies are found in the central region near the coast and the lowest anomalies are found in the northern region near the coast,” the experts explain. Of particular concern is the area from Airlie Beach to the southern edge of the barrier, where the anomalous heat continued for 9-11 weeks compared to 7 in the northern one. As indicated, the longer the heat wave lasts the worse the effects of bleaching on corals. Only after more in-depth investigations will it be possible to understand the actual seriousness of the ongoing phenomenon.

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