(Describer) Under a round logo of a wave, title: Ocean Today. In computer-enhanced video, a red object has circles of light green dots.

(woman) This is a close-up of a coral polyp. These red dots are the individual algae cells-- the symbionts that live inside the coral tissue.

(Describer) ...Amy Eggers.

(female narrator) Coral reefs are gigantic, but corals themselves are very small. And the things scientists like Ruth Gates at the University of Hawaii need to know about corals happen at such small scales that it takes a million dollar microscope to see them.

(Describer) Gates:

(Gates) This is a laser-scanning confocal microscope. It's the only microscope in the world that allows us to image corals live, in simulated future-ocean conditions that are warmer and more acidic. And we can watch the response on the microscope of a living animal. It's remarkable technology.

(Describer) Viewed more closely, the red sections move with blue circles in them.

(narrator) Why do they need to look close enough to see inside a coral? Because corals are in trouble, and the solution to their rescue might be within.

(Describer) White coral stand underwater.

Corals around the world have been declining for some time, but the years from 2014 to 2017 were devastating. Abnormally high water temperatures caused a global bleaching event, only the third ever and the longest in recorded history.

(Describer) C. Mark Eakin:

(man) The past few decades, we've lost about half of the world's coral reefs. In the last three years, we lost another 20% of what remained. The problem is, as the oceans continue to warm, we're going to lose more and more corals. In fact, climate models are predicting that 90% of the world's coral reefs will see temperatures that cause bleaching every single year by mid-century.

(Describer) A computer model shows oceans reaching five degrees Celsius.

(narrator) The reason hot water causes corals to die off is well understood. Corals have algae called zooxanthellae living inside their cells and giving them energy through photosynthesis. The algae can also get too hot, and when they do, they release chemicals toxic to the coral. The coral ejects the algae and turns white, or bleaches. But Ruth and others have found that some super corals bleach less easily or recover faster. Now they can start to see why.

(Describer) Some white coral has light brown pieces.

(Eakin) By using the confocal microscope, scientists can go in, find these corals that are more tolerant to high temperatures, and potentially use these for breeding to try and develop super corals.

(Describer) Gates:

(Gates) These bright green patterns that you see-- those molecules protect the algae. We don't know why they're important in the system, but that's why science is so amazing. We're always looking at discovering new phenomena.

(Describer) Bleached and healthy are compared.

(narrator) They do know that corals can host different types of zooxanthellae, and some of these might be super algae that do better in high temperatures and acidity too. If that's the case, can scientists help to make that relationship even better?

(Describer) Bleached and healthy sit in a tank.

(Gates) One strategy we're looking at is to try to give corals the best zooxanthellae they can possibly have. So can we take the ones that aren't very good at facing temperature out of the system and put back zooxanthellae that are better at facing higher temperatures and surviving?

(Eakin) Corals take hundreds to thousands of years

(Describer) Eakin:

to adapt to warming conditions. We don't have that long. By breeding super corals through the process of human-assisted evolution and finding the best algae to go with those corals, we may have an opportunity to try and do in just a decade or two what the corals would do over hundreds or thousands of years.

(Describer) Pieces grow on a grid.

Over the last 10 years or so, there's been a great advance in using coral nurseries-- fragmenting corals, growing them back, and putting them on reefs. But you can't restore a habitat when the problem is still there. As temperatures rise, we need the super corals-- those corals that can tolerate high temperatures. The challenge for the next scientists and engineers is to find how to grow them faster, grow more of them, plant them fast enough to be able to spread corals out and restore coral reefs all around the world. That's what we need to make a coral comeback.

(Describer) In a microscopic image, red polyps open and close like flowers. Titles: Narrator: Lori Berman. Ocean Today has been brought to you by the Smithsonian Institute in collaboration with the National Oceanic and Atmospheric Administration. Accessibility provided by the US Department of Education.

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Accessibility provided by the U.S. Department of Education.