Saving the worlds coral reefs by speeding up evolution

Vividly coloured coral reefs are a beautiful backdrop in tropical scenes, like living sculptures designed for the jewel-toned fish that glide over and around them.

In Reef Rescue, a documentary from The Nature of Things, we learn that they are biodiversity hotspots that support a quarter of all marine life, including 4,000 species of fish along with crabs, shrimp and turtles. Dubbed “rainforests of the sea,” they stretch from the tropics up to Canada’s east coast.

Over 500 million people around the world rely on these reefs for food, fishing and tourism. Researchers are studying coral-dwelling creatures to develop new drugs. And reefs act as breakwaters to reduce the destructive power of storm waves to protect coastal cities like Miami, Florida. In all, the loss of reefs would trigger a catastrophic loss of biodiversity, and an estimated human economic cost pegged at $1 trillion.

Animal, vegetable or mineral? All three

Each individual coral is a fragile ecosystem — a colony made up of thousands of tiny organisms called polyps. A coral reef is a teeming metropolis of mini-ecosystems built up over thousands of years.

As each polyp grows, they protect themselves with an outer skeleton of calcium carbonate, or limestone, which gives the coral its shape, making it appear like a plant or cactus. Inside live tiny algae which have a symbiotic relationship with the polyps, formed millions of years ago. Just like land plants, algae produce energy from the sun through photosynthesis. They are protected inside the coral and in return, provide oxygen and nutrients for their host. The magical colours of corals are a beautiful by-product of chemicals the algae produce.

But many algae can’t survive the hot-house temperatures of warming oceans, and it’s causing a global catastrophe that some scientists are racing to fix.

Coral in hot water

When average ocean temperatures rise even half a degree, the algae inside the coral polyps start producing toxins. As the coral becomes stressed and expels them into the water, it loses the nutrients that the algae produce. Coral colonies starve and die, leaving behind dead reefs like deep-sea ghost towns.

University of Victoria marine biologist Julia Baum has witnessed the devastation. She’s been gathering underwater photos and video of the coral reefs at Christmas Island for over a decade and was shocked to see a vast section die between 2014 and 2016 as ocean temperatures spiked 2.5 C during a heatwave.

“It was like a graveyard,” she says. “It’s just hard to believe that a whole island can die in less than a year.”

The same heat wave affected vast stretches of other reefs in the Pacific Ocean. Greg Asner of Arizona State University’s Center for Global Discovery and Conservation Science has seen it from his airborne lab over Hawaii — in a plane that can produce 3D images of coral reefs below the waves. In 2015, Hawaii lost over half of its coral in a single month, he says.

Since 2016, successive heatwaves killed over half of Australia’s famous Great Barrier Reef.

These events bleach the coral. But Baum and her team have discovered some hardy colonies which have survived the devastation. “To me, this was almost like a miracle.”

Researchers believe the coral survivors hold the key to helping reefs survive future heat waves. Scientists are racing to identify specimens that can endure warmer water and breeding them to produce what they call “super coral.”

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Super corals could save the future of reefs worldwide

Marine biologist Andrew Baker of the University of Miami has found that under heat stress, some coral not only spew out toxic algae but replace it with heat-resistant algae. It’s one way they’re adapting to climate change.

Now Baker and other scientists are trying to speed up that adaptation, fast-forwarding the evolution of coral in the lab and bringing it to the ocean floor. He’s bringing coral closer to the ocean’s surface to trigger the release of old algae so heat-resistant algae can move in a process called “controlled bleaching.”

The Hawaii Institute of Marine Biology is testing marine biologist Ruth Gates’ revolutionary “super coral” concept, combining the eggs and sperm of heat-resistant coral to produce even more hardy versions of the creatures.

“If we’ve got a really good performer over here and over here, let’s not leave it to chance that their eggs and sperm would meet. Let’s bring them together and make sure they do,” said Gates. “So that’s accelerating a natural process.”

Madeleine Van Oppen and her team at the Australian Institute of Marine Science are raising the next generation of super coral by creating tiny hybrids of different species with heat-resistant strengths in the lab and taking their coral babies back to the Great Barrier Reef. Not all have survived, but amazingly, some have.

“There are hybrids and purebreds alive,” Van Oppen said. “It gives me hope and I just pray that it’s going to be enough.”

Watch Reef Rescue on The Nature of Things.