Can the planet’s coral reefs be saved?

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A. Conservationists have put the final touches to a giant artificial reef they have been assembling at the world-renowned Zoological Society of London (London Zoo). Samples of the planet’s most spectacular corals – vivid green branching coral, yellow scroll, blue ridge and many more species – have been added to the giant tank along with fish that thrive in their presence: blue tang, clownfish and many others. The reef is in the zoo’s new gallery, Tiny Giants, which is dedicated to the minuscule invertebrate creatures that sustain life across the planet. The coral reef tank and its seven-metre-wide window form the core of the exhibition.

‘Coral reefs are the most diverse ecosystems on Earth and we want to show people how wonderful they are,’ said Paul Pearce-Kelly, senior curator of invertebrates and fish at the Zoological Society of London. ‘However, we also want to highlight the research and conservation efforts that are now being carried out to try to save them from the threat of global warming.’ They want people to see what is being done to try to save these wonders.

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B. Corals are composed of tiny animals, known as polyps, with tentacles for capturing small marine creatures in the sea water. These polyps are transparent but get their brilliant tones of pink, orange, blue, green, etc. from algae that live within them, which in turn get protection, while their photosynthesising of the sun’s rays provides nutrients for the polyps. This comfortable symbiotic relationship has led to the growth of coral reefs that cover 0.1% of the planet’s ocean bed while providing homes for more than 25% of marine species, including fish, molluscs, sponges and shellfish.

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C. As a result, coral reefs are often described as the ‘rainforests of the sea’, though the comparison is dismissed by some naturalists, including David Attenborough. ‘People say you cannot beat the rainforest,’ Attenborough has stated. ‘But that is simply not true. You go there and the first thing you think is: where are the birds? Where are the animals? They are hiding in the trees, of course. No, if you want beauty and wildlife, you want a coral reef. Put on a mask and stick your head under the water. The sight is mindblowing.’

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D. Unfortunately, these majestic sights are now under very serious threat, with the most immediate problem coming in the form of thermal stress. Rising ocean temperatures are triggering bleaching events that strip reefs of their colour and eventually kill them. And that is just the start. Other menaces include ocean acidification, sea level increase, pollution by humans, deoxygenation and ocean current changes, while the climate crisis is also increasing habitat destruction. As a result, vast areas – including massive chunks of Australia’s Great Barrier Reef – have already been destroyed, and scientists advise that more than 90% of reefs could be lost by 2050 unless urgent action is taken to tackle global heating and greenhouse gas emissions.

Pearce-Kelly says that coral reefs have to survive really harsh conditions – wave erosion and other factors. And ‘when things start to go wrong in the oceans, then corals will be the first to react. And that is exactly what we are seeing now. Coral reefs are dying and they are telling us that all is not well with our planet.’

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E. However, scientists are trying to pinpoint hardy types of coral that could survive our overheated oceans, and some of this research will be carried out at London Zoo. ‘Behind our … coral reef tank we have built laboratories where scientists will be studying coral species,’ said Pearce-Kelly. One aim will be to carry out research on species to find those that can survive best in warm, acidic waters. Another will be to try to increase coral breeding rates. ‘Coral spawn just once a year,’ he added. ‘However, aquarium-based research has enabled some corals to spawn artificially, which can assist coral reef restoration efforts. And if this can be extended for all species, we could consider the launching of coral-spawning programmes several times a year. That would be a big help in restoring blighted reefs.’

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F. Research in these fields is being conducted in laboratories around the world, with the London Zoo centre linked to this global network. Studies carried out in one centre can then be tested in others. The resulting young coral can then be displayed in the tank in Tiny Giants. ‘The crucial point is that the progress we make in making coral better able to survive in a warming world can be shown to the public and encourage them to believe that we can do something to save the planet’s reefs,’ said Pearce-Kelly. ‘Saving our coral reefs is now a critically important ecological goal.’