News & blog British Science Festival: Resilient reefs Written by Alan Barker, Freelance Writer, British Science Festival Coral reefs are facing an unprecedented threat from rising sea temperatures. But the story’s not all doom and gloom: Heidi Burdett (the Lyell Centre, Heriot Watt) who delivered the Charles Lyell Award Lecture at this year’s British Science Festival, is on the case. Alan Barker took the plunge and listened in. Here’s a thing: coral reefs comprise less than 0.25% of the marine environment, but they’re home to about 25% of all the fish in the ocean. It’s been estimated that coral reefs host up to two million species – perhaps a quarter of all marine life. That’s not just important in itself. Humans benefit from coral reefs in many different ways: tourism, food, even coastal protection. One estimate values the economic value of coral reefs at $30bn annually. But these reefs face an uncertain future. Rising levels of greenhouse gases – CO2, NO2, methane – are contributing to climate change. One critical consequence is that the oceans are warming. And if there’s one thing that coral finds hard to deal with, it’s warmer water. As Heidi Burdett of Heriot-Watt University explained in her absorbing lecture, coral is an animal – or rather a community of animals – living in symbiosis with algae. Raise the water temperature and the algae are expelled, depriving the coral of its principal food source – and its colour. Bleached coral may not yet be dead, but it is starving. If the bleaching continues, the coral will surely die. Mass bleaching events, which can affect hundreds of kilometres of reef, are a major cause of concern – and have been happening more frequently in the past few decades. Reefs have survived ocean warming in the past. And some corals seem particularly resistant to bleaching and might hold clues to creating more resilient reefs in the future. Heidi and her colleagues are investigating the physiology of these hardy corals: what makes them different? Bleached coral may not be dead, but it's starving (Picture: Vardhan Patankar, Wikimedia Commons) The massives, for instance, are – well – massive, and often very old (sometimes, hundreds of years old). Like trees, they lay down growth bands. Heidi and her team take core samples (which we were assured do not harm the coral) and use them to investigate how past temperature changes have affected the coral’s development. Coralliths, in contrast, are free-living, mobile corals that roll around on the seabed until they become too big to move. As they bed down, the underside of the coral dies; if the corallith then gets knocked about by a storm or a big fish, the dead portion rolls into view and can become the substrate for a new reef. Then there’s Heliopora coerulea. As its name suggests, this coral is blue – very blue. There’s only one species, found around the world. And it never bleaches. Does the blue colour protect the coral against sunlight? Does the iron content in its skeleton somehow make it more resilient? Heidi’s team is on the case. Heliopora coerulea in the Maldives (Picture: Frédéric Ducarme, Wikimedia Commons) What strategies does this work suggest for saving the reefs? Perhaps we could transplant new corals onto damaged reefs. It’s a good way to engage a local community, but it’s slow, labour-intensive work – and it involves a lot of glue (yes, that’s how you transplant coral). Maybe we could seed corals with new algae. But spraying algae underwater is pretty hit-and-miss, and corals are notoriously picky about the algae they like. In the end – and here Heidi’s talk became unashamedly evangelical – we need to deal with climate change. We’re all involved in the problem, and Heidi believes we should all take responsibility for the solution. Write to your MP. Find good answers for the climate-change deniers you encounter (and those answers aren’t simple). Calculate your carbon footprint. Heidi shared hers with us; she scores badly on air travel, precisely because she needs to travel to the reefs she’s studyng. Ironically, she’s contributing to the problem she’s trying to solve. It was a brave admission and a reminder that scientists are often more acutely aware of the moral dimensions of their work than we might imagine. Find out more about the British Science Festival here.