Quirks & Quarks·Q&A

New book details race to save coral reefs around the world

Coral reefs support some of the most biodiverse ecosystems on the planet, but lately they've been struggling due to pollution, fishing practices and warming oceans. Oceanographer and science writer Juli Berwald lays out the science happening around the world to save coral in her new book called Life on the Rocks: Building a Future for Coral Reefs.

Scientists farming more resilient coral, building rebar support structures to save reefs worlwide

A diver photographs a coral reef in the Egyptian Red Sea marine reserve of Ras Mohamed on Sep. 4, 2018. (Emily Irving-Swift/AFP/Getty Images)

Coral reefs support some of the most biodiverse ecosystems on the planet, but lately they've been struggling. 

Even though they are only found in one per cent of the ocean, reefs are home to 25 per cent of the world's marine species. But pollution, extreme fishing tactics and warming oceans mean that coral colonies around the world are dying out every year — and many experts fear the worst is yet to come.

In a new book Life on the Rocks: Building a Future for Coral Reefs, oceanographer and science writer Juli Berwald lays out the science happening around the world to save coral. Here is part of her conversation with Quirks & Quarks host Bob McDonald.

This interview has been edited for length and clarity.

You talk in your book about the symbiosis that you see on a coral reef. Tell me about that. 

Coral have this amazing symbiosis with algae. They have algae that lives in their tissues. Those algae photosynthesize and make sugar from sunlight and water and carbon dioxide and they feed about 90 per cent of the sugar they make to the coral animal. With that energy source, the coral make the limestone structures that are their skeleton. Because the coral have teamed up with this algae in such an intimate way, they have become one of the most productive ecosystems on our planet in this really nutrient-poor part of the seas. 

We're hearing a lot about some of the stressors that coral reefs are facing. Can you give me a list? What are some of the big ones? 

Corals evolved in times when there weren't very many nutrients around. Now that we have a lot of pollution in the form of runoff from fertilized fields, the corals don't like it. They don't handle the extra nutrients very well and that's led to a lot of coral diseases. 

Berwald's book, Life on the Rocks: Building a Future for Coral Reefs. (Penguin Random House)

The other problem is illegal fishing and overfishing. Illegal fishing can actually physically destroy coral reefs with dropped anchors and dredging along corals. Then there's a kind of fishing … called blast fishing, where some fishermen will actually throw bombs onto the reef. 

But ultimately, the biggest problem for coral is climate change. Scientists don't understand it, but for some reason, the coral-algae symbiosis has evolved to be very close, maybe about two degrees away, from its thermal tolerance. When we have heat waves going through the ocean, which we do more and more frequently now that we've heated up our planet, the coral algae symbiosis falls apart.

The algae leave the coral, they take all their colour with them, and so the coral look just like a piece of clear tissue spread over a white skeleton. So, they look bleached. But when those algae leave, they don't just take their colour, they take all the nutrition that they used to be feeding the corals, all that sugar. All of a sudden, the coral are on these starvation rations. If this high temperature goes on for too long, the coral will die. 

Is there any indication that coral reefs are adapting to tolerate the warmer waters? 

Yes, and that was one of the funnest things that I discovered in doing the research for this book. The algae that the coral currently use is very particular about the temperature. Like I said, they leave when the water increases by about two degrees for a couple of weeks. But sometimes when the corals are being re-colonised as the water cools down, they're actually accepting a different algae. That algae has about a degree and a half higher tolerance for heat.

But there's a little bit of a tradeoff in that this new species of algae only feeds the coral about 60 per cent of the sugar it makes. It's a more selfish partner, but it can handle a higher temperature. It may be enough to keep the coral going as our seas warm. 

This picture taken Sep. 4, 2018 shows a view of a bommie reef in the Egyptian Red Sea marine reserve of Ras Mohamed. (Emily Irving-Swift/AFP/Getty Images)

Well, let's go through some of the solutions, because your book is not all about the problems with the coral reefs. You do look at what people are doing to try to save them. Tell me about some of the genetics work that's being done to help the corals adapt. 

One of the most amazing things about corals is that they have a ton of genetic variability, and it turns out that every time there's a bleaching, most of the corals will bleach and die, but not all of them. There's always a few that seem to survive. Scientists are looking at those corals and asking, 'What makes them different? What is it about their genetics that allows them to survive?'

As we start to restore coral reefs, they're asking 'Should we be growing these corals, helping them proliferate in our labs and in these underwater nurseries and using these more robust corals to replant coral reefs with?' Those projects are happening really all over the world. 

What about restoration projects that actually rebuild damaged reefs? 

So not every restoration is successful, but I saw some that were mind-blowingly successful. I guess maybe the one to highlight is in Indonesia, off of this island called Sulawesi, which is a little bit northeast of Bali. It's a very big island and it has a huge shelf where there's a ton of coral reefs in shallow water. 

Near this part of Sulawesi, the Mars Candy Bar Company actually had a chocolate factory. They noticed that a lot of the people who were working in the factory had for years been adding to both their income and their source of protein by fishing, and their ability to do that was just declining as the reefs were degrading. 

So, Frank Mars, the head of the factory, wanted to find a way to help restore some of these reefs and do it in a way that is not technologically difficult, that can be used on other tropical islands and isn't terribly expensive.

Reef stars, developped by Mars Inc. in YEAR, are being used to help restore coral reefs off the Indonesian island of Sulawesi. Reef stars are made of rebar coated in boat resin and local sand with fragments of coral tied on. (The Ocean Agency)

They came up with this idea called 'reef stars.' What you do is you just tie fragments of coral that have been broken off naturally from the reef onto these reef stars in a certain pattern. And then you can plant, say, 100 or 200 or 500 stars at a time. They've restored hectares of reef this way. 

When I got to dive on these reefs in Indonesia, the coral grew so well in this region when they're given the opportunity that you could hardly see the reef stars at all. There were fish everywhere, sea turtles, sharks. I mean, you couldn't even see the restoration at all. So it's a great feeling to know that, under the right conditions, these coral are really resilient and the ecosystem is really resilient.


Q&A edited for length and clarity. Produced by Amanda Buckiewicz. Click on the link at the top to listen to the full interview with Juli Berwald.

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