MAJURO, Marshall Islands—Perched on the bow of an aluminum landing craft, Anne Cohen gazed a few yards ahead of the vessel toward a yellow robot gliding across the emerald Majuro lagoon.
The unmanned surface vehicle, called Yellowfin, was quickly becoming one of the coral researcher’s most dependable guides in these Central Pacific waters.
“She’s the best dive buddy,” said Cohen, a tenured scientist at the Woods Hole Oceanographic Institution in Cape Cod. Programmed to navigate to a precise set of coordinates, the robot cut through small swells like a tiny sailboat without a mast, directing Cohen toward a destination she had traveled thousands of miles to revisit.
When the robot finally paused, hovering in place, Cohen recognized it as her cue. Somewhere below should be a patch of reef she’d been observing over the last few years, and she was eager to see how it was faring. Each visit carried a growing weight of uncertainty.
Since 2023, record-breaking marine heat waves have swept through the tropics, fueling the most severe global coral bleaching event ever recorded . More than 80 percent of the world’s reefs have been impacted in at least 83 countries and territories. Corals have been so stressed by the extreme temperatures, they’ve expelled the tiny algae living inside their tissues that provide them with food and their brilliant hues, leaving them pale, ghostly and struggling to survive. Many have not recovered.
Cohen hoped the reef beneath her might be different.
She yanked on her black and yellow snorkel fins, spit into her mask so it wouldn’t fog underwater and slid off the boat, her slight frame barely making a splash. Within seconds of peering into the blue, she let out a squeal muffled by her snorkel, astonished at the scene unfolding beneath her.
Towering pinnacles of chestnut-colored tabletop corals rose from the sandy seafloor like trees, their broad plate-like canopies sheltering fish hiding in their shadows. Dense thickets of staghorn corals stretched in every direction, their golden antler-like branches twisting across a sprawling reef extending as far as the eye could see, bursting with shades of mustard yellow, pink and lavender pastels.
“It’s like a wonderland,” Cohen said, popping her head above the surface, beaming. “I feel like Alice.”
Anne Cohen has been studying coral reefs and climate change for 30 years at the Woods Hole Oceanographic Institution. Credit: Tim Briggs
In today’s oceans, the scene felt almost surreal, said Cohen, 62, who has spent the last 30 years studying coral reefs and the impacts of climate change on marine environments.
But it was a confirmation of something she had long believed: that even as hotter temperatures devastate coral reefs, some still possess an extraordinary ability to endure. She was determined to find out how.
Unlocking the secrets behind their resilience, she said, could one day help scientists and conservationists restore, or even cultivate, reefs better equipped to survive a warming planet.
Searching for Super Reefs
Over the last decade, a significant part of Cohen’s research has focused on tracking down these reefs that are somehow defying the odds.
In 2018, she started a project dedicated to this search called Super Reefs, named after a number of reefs she’d encountered around the world that seemed to be thriving even while others nearby bleached or died.
“We saw these corals that were behaving as if there was no heat wave at all,” she recalled. “I kind of felt like there was Superman or Superwoman coming in there and flexing their muscles, being super, super strong.”
Three years later she launched a joint global initiative with The Nature Conservancy and Stanford University aimed at not only finding heat-tolerant communities, but also protecting them.
Even the hardiest of reefs are not invincible, she said.
Marine heatwaves have caused many reefs in Majuro to bleach in recent years. Yet, some reefs have shown remarkable capacity to recover from, or resist, such heat stress. Credit: Tim Briggs
Coastal development projects such as ports or harbors that require dredging can bury corals beneath sediment. Agricultural runoff, sewage and plastic pollution introduce harmful pathogens and excess nutrients that spark coral disease or toxic algal blooms that suffocate the tiny animals. Bottom trawling—a fishing method that drags weighted nets across the seafloor—can crush entire reefs, while dynamite fishing can shatter centuries-old coral colonies in seconds.
“That would be like taking a sledgehammer to crush a hermit crab,” Cohen said.
Already, the world has lost more than half of its coral reefs to the combined pressures of climate change and other human activity. Some scientists warn that without significant intervention, more than 90 percent of tropical reefs could disappear in the next 25 years.
The goal of the new Super Reefs initiative was to specifically identify coral strongholds in places where governmen…
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