Reef Madness

It was mid-summer, 2023, when Dr. Carly Kenkel realized her experiment wasn’t going to work out. Kenkel, a professor of marine biology at the University of Southern California, was in Florida, checking tanks of baby mountainous star corals she had bred herself. That year, across the Caribbean, the majority of corals had died in an historic mass bleaching event, as water temperatures reached never-seen-before highs. It was a once-in-66-million-years heat wave. 

Kenkel’s experiment involved selectively breeding coral specimens that appeared more resilient to bleaching to see if their offspring would be even stronger, in an attempt to strengthen the species in the face of climate change. Instead, the offspring of the stronger corals were weaker than their parents, and in fact weaker than average. 

“The corals have been experiencing stress to such a degree that the parent corals had to invest so much of their stress tolerance already — they don’t have a lot left to invest in the quality of their eggs,” she said. 

The following year — 2024 — was nearly as catastrophic, with water temperatures reaching over ninety degrees on the warmest days. Without enough time to recover, numerous species of corals endemic to the Caribbean could die in the next bleaching event, which is likely to occur in the next several years. Without the reefs, fishing and tourism industries across the region would dissolve and local economies would suffer, not to mention the potential loss of biodiversity. 

With governments in the Caribbean failing to respond to the crisis, scientists are split in their attitudes towards the right path forward; most are wed to restoration efforts, but Caribbean corals breed ineffectively, Kenkel says, so bouncing back after successive years of damage is not a feasible solution. Dr. Ilsa Kuffner, a scientist with the US Geological Survey, said her work placing shading tiles on Elkhorn corals to lower the water temperature has not been enough to save the species.

”When they’re adult colonies, they’re the size of cars, or school buses,” she said. But the reefs don’t look like that now, she said, “because they’re all bleached.”

One scientist has a more radical idea to save the reefs. Dr. Misha Matz, a professor of marine biology at the University of Texas at Austin, is going against the conventional approach and trying his own experiment. Unfortunately, it may require that he be the Caribbean reefs’ executioner as well as their savior. Matz’s plan, known as “coral migration” or “rewilding,” involves transporting foreign species of corals from other oceans around the world and planting them in the Caribbean. Foreign species, like those native to the Persian Gulf which have evolved in an environment prone to turbulent temperatures, are far more resilient to temperature spikes and would spread quickly and widely, Matz explains, while also being more resistant to damage caused by bleaching, hurricanes, boat traffic, and trash. 

The problem with breeding native corals in a lab, Matz continues, is that once placed in the wild, they’ll still be unable to breed effectively and thus will ultimately die out. “Once you know that the old reef is gone, then it’s totally valid to consider a replacement species … In the Pacific, it takes [corals] only seven or eight years to bounce back [from a bleaching event].” (Such corals are such prolific breeders that even when an old reef is bleached, there’s a sufficient supply of coral spawn to start a new reef.) 

Matz believes that even if a reef is not completely dead, if it’s clearly on its way out, then it’s time to start introducing replacements. He says the recovery capacity of foreign corals is “remarkable” and the new reef would be colorful, with plenty of interesting shapes of corals for both people and fish to enjoy (fish appear to not be picky about the type of coral they live amongst, only that basic structures of shelter exist). The first coral he would like to introduce in the Caribbean, a type of Table Coral, creates huge mushroom-like structures with flat platforms at the top. The only issue: corals are prone to battles for territory, and the foreign corals could entirely displace the Caribbean corals, speeding up their extinction. There is also the possibility of unforeseen changes to water conditions introduced by the new species. Matz understands the finality of his solution — after an invasive species is planted, there will be no way to go back. The solution requires an acceptance that the Caribbean reefs will never return to health and that their death is ensured. 

“Our main concern right now is the risk to the remaining corals surviving in the Caribbean,” Matz says. 

Matz expects that, in the next few years, consensus will swell around his idea. He is already in communication with fish and wildlife authorities in Florida, who seem open to his plan to begin planting a test group of foreign corals in northern Florida, where current patterns would hopefully prevent them from spreading to the rest of the Caribbean Sea. As soon as waterfront property owners and governments see that the new corals can form a successful reef, Matz expects foreign corals will spread quickly through the region in the next few years. 

“There’s no legal framework for this [coral migration], which could be a problem,” Kenkel said. “But it’s definitely something the coral restoration community is talking about, in light of the disaster that was last summer in the Caribbean.”

Matz’s idea holds implications not just for the Caribbean, but for the world, as climate change affects every ecosystem. His plan would further normalize the idea of introducing foreign species into a suffering ecosystem in the hopes of filling a gap. However, these actions would permanently alter the natural order: there could be unseen changes to the types of algae or microorganisms present in the region, and if by some chance, years down the line, a miracle solution to the Caribbean coral breeding problem were discovered, there would be no feasible way to get rid of the foreign corals and replace them with natives. Matz argues, with climate change, humans have already meddled too far to go back, and these kinds of drastic solutions are now necessary. 

“It won’t look like a Caribbean reef, but it will be a great reef,” Matz says. “They’ll bleach, they’ll die, but they’ll come back.”