Scientists follow the endangered coral reef in Florida | Science

THE FLORIDA KEYS TREF TRACT-Earlier this month, Lauren Toth, coral geologist specialist at the US Geological Survey (USGS) in St. Petersburg, Florida, decided to learn how much time in Florida, 6 km to wide of Key Largo. coral reef is gone.

Around the world, warming oceans kills coral. In Florida, Toth and others discovered that heat-induced bleaching was only the latest in a long series of insults that have immobilized the growth of the reef and the lobster. have made them vulnerable to erosion and rising seas. As a result, the coral reef – the third longest in the world – is not just dying. It seems to be disappearing.

The challenge is a 320 km long rampart that protects the Keys from the waves while providing a habitat for fish and an attraction for tourists. Recent measurements by Toth and his colleagues have confirmed that coral is eroding several millimeters a year in some places. Now, she and others are studying the entire reef to find out how fast and where it is getting lost.

Warming, disease and pollution on the Florida reef have recently had even greater consequences than other iconic reefs, such as the Great Barrier Reef, in Australia. "We have lost 90% of our coral cover in recent decades," said Erinn Muller, a coral biologist at the Mote Marine Laboratory in Sarasota, Florida. Some species, such as the fast-growing Elkhorn coral with its broad, distinctive branches, have almost disappeared. A crowd of other people died while a disease called stony coral tissue loss had invaded the Keys. "The latest living corals are being hammered," says Derek Manzello, an oceanographer in a laboratory of the National Oceanic and Atmospheric Administration in Miami, Florida.

Yet, Toth and his peers have shown that Florida's corals have not been healthy for millennia. Basic samples of the reef record that he ceased to grow 3000 years ago. The Florida Reef is located near the northern temperature limit for corals, and Toth and his colleagues reported in a study last year that a cooling trend around this period was likely making the waters more difficult. prone to cold snaps that would periodically kill the corals, leaving the reefs at a delicate tipping point.

Now, although cold spells still occur, global warming is bringing warmer summers, resulting in bleaching and massive mortality. It also raises sea level. Healthy corals easily cope with rising sea levels and grow with rising sea levels. But Florida's sick reefs are unlikely to keep pace. Anecdotes abound in flat eroded reef plates.

The data, however, are rare, with one exception: in 1998, USGS scientists drilled stems in 12 dead coral colonies at one site, in the hope of measuring the size of the coral reefs. erosion. Recently, a USGS team led by Ilsa Kuffner and Toth revisited the stems and used the cement that holds them in place as a point of reference. In their work close to publication, they found that dead corals erode by 5.5 millimeters a year, nearly double the rate of sea level rise, as they are shredded by parrot fish and other species.

Toth is now trying to get a broader vision by taking advantage of the bars that Florida State scientists have incorporated at 46 sites along the Keys as benchmarks for an annual photographic survey. On many of these sites, the epoxy that cements each stem in place, once flush with the coral, now remains due to erosion. To get more accurate measurements, Toth and his colleagues developed a portable tool that can sit on top of the stakes.

On this morning of April, she and a colleague were testing the device, floating above a rocky, mountainous starry coral and a massive starry coral, with a fleeting ephemeral observation. 39, a staghorn. The silvery tits, the red grouper and the snappers seemed to watch the scientists working. Each cane presented its own challenge. Some were covered with small fire corals, which divers dislodge with hammer blows. Others had been co-opted by sponges or, in one case, had fused with the spine of a soft fan-shaped coral. When a coral could be damaged or a sponge crushed, scientists failed to measure it.

"The prototype works," Toth said as he climbed into the boat. In this case, the canes recorded little erosion, perhaps because the reef was already chunky. "Once flat, it will probably not be targeted [by fish] She added that this summer, photographic survey divers in Florida will use the USGS tool to measure about half of the rushes at each site, giving a more complete picture of the decline of the reef.

For coral biologist Alina Szmant of the University of North Carolina at Wilmington, Toth's work confirms that the reef is doomed, with assaults submerging a fragile ecosystem. "I do not want to give up, but you have to be honest with yourself," she says.

A patchwork of restoration efforts, mostly from non-profit groups, continues on the reef, often aiming to replace dead coral with heat-resistant grafts. Supporters should temper their expectations, said Toth: "If these reefs do not develop for 3000 years, it will be very difficult to get reefs like those elsewhere in the Caribbean."

Toth still hopes that some live corals can be saved. But she says that biologists must introduce not only heat-resistant or disease-resistant corals, but also species capable of building a structure, such as staghorn or elkhorn. It is also time, she adds, to think about safeguarding the structure of the reef and the services it provides, even if its coral dies. "How can we avoid losing what has been built in the last 8,000 years?" she says. "Because we have not yet 8000 years to rebuild it."