2020 Great Barrier Reef Bleaching Event Is Most Widespread to Date
Professor Terry Hughes, director of the Centre of Excellence for Coral Reef Studies at James Cook University, spent nine days in a plane surveying 1,036 reefs from the air, The Guardian reported. He found that 25 percent of the overall reef was severely bleached. What's more, he observed bleaching in the north, center and south of the reef for the first time.
"It's the first time we've seen severely bleached reefs along the whole length of the reef, in particular, the coastal reefs," Hughes told The New York Times.
#GreatBarrierReef research: First the north, then the middle, now widespread #coral bleaching including in the sout… https://t.co/7O3D47sbrv— Terry Hughes (@Terry Hughes)1586207744.0
The Great Barrier Reef has suffered six mass bleaching events due to warmer than normal ocean temperatures: in 1998, 2002, 2006, 2016, 2017 and now 2020. While the 1998 and 2016 bleachings occurred during El Niño events, a natural climate variation that brings warmer than average ocean temperatures to the region, the 2002 and 2017 events did not, The Washington Post pointed out. Neither did this year's, but it is the second most intense after 2016's. This suggests warmer temperatures caused by the climate crisis are ultimately driving these events.
"It's now clear that we can have major bleaching events caused by global climate change alone with no tropical forcing," Mark Eakin, coordinator for the National Oceanic and Atmospheric Administration's Coral Reef Watch program, told The Washington Post.
Coral bleaching occurs when heat stress causes corals to expel the algae that live within them, providing them both with food and their bright colors. When the algae leave, the corals lose those colors. If the algae stay away for too long, the corals can die.
2016 and 2017's bleachings together killed around half of the corals in the reef. But Hughes told Australia's ABC News that he didn't know how deadly this year's bleaching would be. He told The Guardian that the north and central portions of the reef would probably see less death because the less heat-resistant corals had already died off in 2016 and 2017.
But the south, which remained relatively untouched in previous years, was a different story.
"They hadn't bleached before, which means there are more corals and more of the corals that are particularly susceptible to heat stress," he told ABC News.
I'm not sure I have the fortitude to do this again. It's heartbreaking to see the #GreatBarrierReef decline so fast. https://t.co/LHgP5cIAQW— Terry Hughes (@Terry Hughes)1586230512.0
This means the makeup of the reef is changing, but some of the losing corals include branching corals, which provide important habitat for many fish.
"Branching corals make all of the nooks and crannies that the rest of the biodiversity — the fish and so on — depend on," he told ABC News. "So having fewer and fewer corals is having a much broader effect, not just on the corals themselves, but in the broader ecosystem."
Hughes told The Guardian that only urgent climate action could save the reef.
"It's not too late to turn this around with rapid action on emissions," he said. "But business-as-usual emissions will make the Great Barrier Reef a pretty miserable place compared to today."
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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By Daniel Raichel
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