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  • Imagine scuba diving around the corals of Great Barrier Reef.

  • You are now probably picturing vibrant colors and a bustling ecosystem.

  • But if you decided to visit right now, you’d mostly be seeing the whitish skeletons of

  • corals.

  • Last week, the Australian Coral Bleaching Task Force announced that they’d completed

  • aerial surveys of about 4000 kilometersworth of reefs near Australia and Papua New

  • Guinea.

  • And what they found was not good news.

  • Out of the 520 reefs they surveyed, all but 4 showed signs of coral bleaching.

  • Coral is the foundation of reefs that provide food and shelter for thousands of species,

  • from shrimp to sharks to sea turtles. It’s thought that about a quarter of all marine

  • life depends on the coral reefs in some way.

  • Coral is made of tiny transparent animals called polyps, with thousands of them in each

  • chunk. The polyps produce calcium carbonate -- a white mineral -- which forms intricate

  • crystal skeletons.

  • But most coral can’t survive alone. To get the energy and nutrients they need to grow,

  • the polyps team up with algae called zooxanthellae.

  • The polyps provide a home and the basic ingredients the algae need to survive. Then, the algae

  • use sunlight and photosynthesis to convert these into more complex nutrients like sugars

  • -- which the polyps then eat too.

  • These algae come in all kinds of different colors, which is why coral reefs are normally

  • so colorful.

  • But when conditions change -- like when the water temperature gets too high -- the coral

  • goes into a kind of shutdown mode.

  • The algae leave, taking their bright colors with them and leaving behind those pale calcium

  • carbonate skeletons.

  • This year’s El Niño weather pattern, combined with global warming trends, raised the ocean

  • temperatures around the Great Barrier Reef -- which is what’s causing the bleaching.

  • Since June 2014, bleaching has been happening in coral reefs around the world, which is

  • why scientists are calling this a global bleaching event, the third ever recorded.

  • When the oceans cool again, the algae can often recolonize, reviving the coral.

  • But sometimes they can’t move back in. It’s too soon to tell how much long-term damage

  • there will be, but scientists are estimating that about half of the bleached corals will

  • die.

  • The reefs can grow back, but theyll need time, and waters that stay at the right temperature.

  • And as oceans continue to warm, the coral might not get that chance.

  • In slightly more positive news, scientists have discovered the 3D structure of the Zika

  • virus -- almost down to the atom.

  • When we last talked about Zika, back in February, researchers didn’t know much about the virus

  • -- just that it might be responsible for the sharp increase in Brazilian babies born with

  • a neurological condition called microcephaly.

  • Since then, scientists have made some progress when it comes to understanding how Zika spreads,

  • and how it affects the human body.

  • And last week, a team at Purdue University in Indiana published the 3D structure of Zika

  • in the journal Science.

  • So, here it is!

  • It looks kind of like a little pom-pom, or some kind of candyit might even be cute

  • if it wasn’t Zika Virus.

  • It’s also very colorful, but the virus itself, of course, doesn’t actually have those colors

  • -- they were added to the image to help show the different parts of its structure.

  • The researchers used a form of microscopy called cryo-EM, where they freeze the virus,

  • then shoot high energy electrons at it. By studying how those electrons get scattered

  • or absorbed, they were able to piece together a digital 3D model.

  • Knowing what Zika looks like in so much detail is an important step in figuring out how the

  • virus works -- and hopefully, how to protect people from it.

  • So, what does this little pom-pom tell us?

  • Zika’s surface looks roughly spherical, but it’s actually closer to an icosahedron

  • like the D20 you’d use in games like Dungeons and Dragons.

  • The protein coating that forms the icosahedron protects the genetic material inside.

  • But researchers are especially interested in those red nodules, which are carbohydrate

  • groups attached to short protein loops.

  • Now, it’s not unusual for viruses to have something like thisit’s how they latch

  • onto our cells and get inside.

  • But this little loop is very different from the loops on other viruses related to Zika,

  • and varies between Zika strains.

  • So, studying these regions in particular could be critical in understanding how Zika affects

  • humans -- for example, the loops might be allowing Zika to infect different kinds of

  • tissue, including the brain.

  • Of course, knowing Zika’s structure doesn’t guarantee a cure or vaccine. But if were

  • going to fight something, it helps to know what it looks like.

  • Thanks for watching this episode of SciShow, which was brought to you by, you guessed it,

  • all of our patrons on Patreon. If you are one of those people, thank you very much.

  • If you want to be one of those people, you can go to patreon.com/scishow to help support

  • us. And don’t forget to go to youtube.com/scishow and subscribe!

Imagine scuba diving around the corals of Great Barrier Reef.

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大堡礁的白化現象和寨卡病毒的最新進展 (Bleaching in the Great Barrier Reef, and a Zika Update)

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    羅紹桀 發佈於 2021 年 01 月 14 日
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