[SciShow Intro Plays]

Hank Green: 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 kilometers’ worth 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 they’ll 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 candy... it 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 this – it’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 we’re going to fight something, it helps to know what it looks like.

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