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As early warning system of the oceans, coral reefs have been ringing for years. They have been laundered by marine heat waves and have been killed en masse by a combination of factors including pollution, overfishing, acidification and climate change.
But now scientists in Florida and other tropical regions around the world are trying to stop decay by creating coral "nurseries" in which young populations can be raised under controlled conditions before being planted on trees. bare reefs.
Off the southern tip of Florida, a large marine operation has been created in which corals are carefully grown on fiberglass trees anchored and planted on the coral reef.
"The idea is to do everything we can now to give these coral populations a chance to fight," says Jessica Levy, Program Manager at the Coral Restoration Foundation. "If you do not put the lost material and diversity back, people will collapse and disappear. For reefs, you observe a global extinction of the ecosystem if things do not change quickly.
Florida has the third largest barrier reef in the world, with nearly 1,400 species of plants and animals and 500 species of fish, but the reef is rapidly disappearing. Research has shown that about half of the reef has disappeared in the last 250 years. The cover of the acropora, the main genus of corals that build reefs, dropped by 97%. "The reef is pretty barren right now," says Levy.
The diseases are numerous and go back decades. A burgeoning Florida population and mass tourism have resulted in water pollution and direct damage to the corals, while agriculture has sent torrents of nutrients into the reef.
Although regulations have limited some of these local risks, climate change remains a major threat. In 2014, a spike in water temperature led Florida corals to bleach – when a reef expels its symbiotic algae under heat stress, whitens and potentially dies. This happened again in 2015, when the corals of the planet were hit by prolonged bleaching of the planet. The Great Barrier Reef was cooked to the point that she would have felt death.
The world is on the right track for an increase in temperature that will easily eliminate most coral ecosystems, a scenario that would eliminate an essential nursery and shrub for countless marine species, reduce fishing and eliminate a buffer zone. planet is warming up.
"The prospects for the Florida reef are pretty grim," says Kim Cobb, coral expert at the Georgia Institute of Technology. "The threats are overwhelming. Just as the reef goes beyond decades of systemic problems, it is increasingly threatened by climate change.
The Coral Restoration Foundation has expanded coral replanting activities as the situation worsens and the underwater trees of the foundation become sought-after items for stressed reefs around the world.
Partnerships have been created to provide trees in places such as Jamaica and Colombia. A chartered fishing company in Mexico is in talks to do the same thing. This month it was announced that 100 corals had been successfully planted on the Great Barrier Reef, the largest living structure in the world, using coral frames.
The operation took place after tropical fish collector Ken Neidermeyer noticed a rare type of coral called stylophora growing on his farm in 2003. A loophole in the laws on endangered species meant that "no one in the world" would ever be able to see it. it had to be kept. coral fragments.
Neidermeyer hoped to repel enough coral to begin repairing the Florida reef. Initially, the fragments were mounted on recessed concentric blocks that mimicked reefs. But the real breakthrough occurred in 2011 with the development of manufactured trees on which dozens of pieces of coral can be hung from the branches.
Supported by funding from the federal government and relevant donors, the foundation now has approximately 700 trees in seven nurseries along the reef system, to Ernest Hemingway's former hideout in Key West.
The recovered fragments of wild coral are cut into finger-sized pieces, sorted into genomic types and threaded into fiberglass and PVC trees, which are anchored to the bottom of the sea and tagged with a float . Beside the staghorn and elkhorn corals, which gently sway on the current lines, are corals covered with blocks mounted on nearby platforms.
This environment allows corals to grow three times faster than normal. Nevertheless, it takes them up to nine months to reach the size of a small football. At that time, they are attached to a suitable reef with the help of a special putty.
Diversity is key, says Levy. While other projects are experimenting with heat-resistant corals, able to cope with occasional warming of the waters, the foundation hopes that a range of coral candidates will produce survivors. "We do not want to put all our eggs in the heat tolerance basket," she says.
The goal is that corals take root, connect and reproduce. So far in 2018, more than 18,000 corals have been planted on the reefs, double what was done each year five years ago. About eight in ten planted corals survive at least a year.
This work is laborious and sometimes heavy. Trees need to be cleaned regularly and nearly 300 coral genotypes out of nine species need to be sorted and tagged. Repelled corals can be quickly eliminated by heat stroke, storms or disease. Hurricane Irma stripped coral trees, although the structures themselves were almost all spared.
"We lost some stock with Irma," says Levy. "This work can be very difficult and very rewarding. You plant corals and watch them grow for several years, then something out of control, such as bleaching, can occur.
"It makes us do the numbers – the more corals we have, the greater the diversity and the more likely it is that something will happen after the ongoing stress."
The largest nursery, located five kilometers from the Key Largo coast, has about 500 trees, which look like giant and outdated television antennas. Rowed coral and elkhorn coral hang trees just 10 feet under the water.
A constellation of marine life, such as trumpet fish, porcine fish and trigger fish, sneaks between the trees. A nearby reef site is scattered with replanted corals bearing the tags of the Coral Restoration Foundation, although the overall coral cover is small.
The dark scene is complemented by stands of dead pillar coral, ravaged by a bacterial disease that swept the Keys last summer. A nearby cerebral coral is divided by white sawtooth lines, which is further evidence of the disease. The origins of many coral diseases are vague but at least one major epidemic has been linked to human faecal waste: the Keys have acquired a fully functional sewage system only in the last decade. Recent research has shown that these diseases will worsen as the oceans warm up.
The magnitude of the foundation's task is "monumental," says Cobb. But restoration work could help provide a lifeline to the reefs, she says.
"The corals managed to cross the impact that killed the dinosaurs," she says. "I think some corals will get through, the question is how much will remain. Important work is very promising. There will not be one solution, but a basket, of which we can only guess. "
Another form of reef renovation took place in the Bahamas, where scientists collected massive reproductive material – when corals massively release plumes of spermatozoa and eggs – to help produce more abundant offspring. more powerful.
"We've done well," says Joseph Pollock, coral strategy director for the Caribbean division of Nature Conservancy. He participated in a recent spawning event off Cape Eleuthera, which resulted in more than one million coral larvae. "It's not a solution in itself, it's part of a suite of tools that can be used. If you do not work on stressors, from climate change to coastal pollution, you might as well not do that job. "
Back in Florida, the Coral Restoration Foundation is forming a new group of interns, who will contribute to public awareness efforts. In the foundation's offices, fiberglass trees are cleaned and plans are made to inspect a nursery while the sky is clear of a tropical storm. The work, in the light of changing weather conditions, seems endless.
"I'm not ready to give up," says Levy. "Nobody wants these reefs to die as they please, so I'd rather do something and sit and watch everything die."
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