Can “immigrant” corals save Florida’s dying reefs?

By Rob | August 31, 2025 |

Scientists are testing hybrid elkhorn corals bred from Florida and Honduras parents in the wild for the first time. The experiment could reshape both reef survival—and conservation politics.

Fig. 1. Summary of coral species, collection site information, coral breeding and heat stress trials (A) Map of the Great Barrier Reef showing the sites of coral collection, a heatmap showing locations and environmental conditions for collection sites (see Supplementary Figure S1 and Supplementary Table 1 for full site information; MMM = maximum monthly mean, DHW = degree heating weeks, BAA = bleaching alert area), and images of the three study species: A. kenti, A. hyacinthus and G. retiformis. (B) Diagram of coral breeding of the three coral species and the resultant families. Numbers and symbols indicate the number of dams and sires used in the crosses. (C) Diagrams of the experimental setup for the three heat stress trials: adults (duration = 7 days for A. kenti and A. hyacinthus, 11 days for G. retiformis), larvae (duration = 61 h), and juveniles (duration = 31 days; D1a = Durusdinium trenchii, SS = heat-selected Cladocopium goreaui, wild = symbionts within Jewell reef sediments; see Methods 2.3 Adult heat stress experiment, 2.4 Larval heat stress experiment, 2.6 Juvenile heat stress experiment for full details).

By Warren Cornwall in Anthropocene

August 20, 2025

Coral isn’t exactly a migratory species. Many have exoskeletons that seem more like sculptures than living organisms. But right now, Florida scientists are watching closely to see if an unusual experiment in coral migration pays off.

As the state’s coastal waters warm in the August heat, it will be the first hot-water test in the wild for fledgling elkhorn corals that trace their lineage to parents from Honduras and Florida, two parts of the Caribbean so far apart that the corals would normally never meet.

“It will be very interesting to see how they do,” says Andrew Baker, a coral ecologist at the University of Miami.

This isn’t just a biological experiment. It’s also a political one. This is the first time that Florida regulators have permitted the release of coral with genes imported from another part of the region. And if scientists like Baker get their way, it won’t be the last.

In a late July piece in Science magazine, Baker and other coral scientists laid out the need for such measures, and the kinds of political and institutional changes that might help make it easier to repeat.

Dubbed “assisted gene flow” (AGF), it’s the latest example of the kinds of gymnastics being done by conservationists and scientists to help populations try to outrun changing environmental conditions by giving a boost to migrations. In some cases, this means literal changes in migration, like researchers in Europe who carried birds further north. In other cases, like the Florida coral, it means moving genetic material around.

If there were ever a population in need of some outside help, it’s Florida’s elkhorn coral. Decades of pollution, boat damage, diseases and warming waters have wiped out most of the natural reefs created by spiky elkhorn and their more sprawling relatives, staghorn coral. Those two species have declined by 97% in Florida since the early 1980s.

Today there are just 158 genetically unique individual Florida elkhorns in existence. And just 23 of them are found in the wild.

The danger of such a small genetic pool was highlighted in 2023, when a record-setting underwater heatwave in Florida devastated many of the remaining patches of elkhorn coral – both naturally occurring ones and ones raised in tanks and then planted in the water to rebuild reefs.

Recommended Reading:

Algae “perfume” fused with high-tech materials holds promise for growing coral

Scientists drew one big conclusion from the wipeout: They needed more genetic diversity to give these corals a chance to evolve to cope with a warmer world. In part, that means a growing emphasis on sexual reproduction between Florida coral in aquaculture facilities to create more genetically unique offspring. In the past, coral planting projects relied chiefly on clones of existing individuals, created by breaking off a bit of a coral exoskeleton – really a colony of genetically identical coral polyps.

But even more genetic diversity could come from other elkhorn populations elsewhere in the Caribbean, such as the ones from Honduras. There, elkhorn coral are thriving in water that is warmer and more polluted, says Baker.

In a lab, the scientists created what Baker calls a “Flonduran” coral, using genetic material collected from spawning Florida and Honduras corals. The offspring eventually took root on small hockey puck-like discs, ready to be placed on the ocean floor.

“The hope is that some of these offspring that are now a year old are actually going to be better able to deal with Florida’s warm summers,” says Baker.

But before researchers could put the offspring in the water, they needed to navigate a regulatory thicket built to control the movement of species across political boundaries. That included permission from the Florida Fish and Wildlife Conservation Commission. Before that it had taken a year to obtain permits to bring chunks of the Honduran coral to their Florida lab.

In a warming world where conservation scientists see an increasing need to intervene in natural processes, today’s political rules can be hindrance, Baker and colleagues warned in their Science paper. The international agreement governing the cross-border transport of species, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), is one hurdle scientists might have to clear. In the U.S. there’s the Endangered Species Act. Then there’s the Nagoya Protocols, a less-widely used agreement with recommendations for how genetic material is shared across borders.

When it comes to coral, Baker and co. have some advice on how to streamline these systems, while avoid the kind of abuses that can abet a black market in endangered species, the introduction of unwanted pests, or the hijacking of one country’s genetic legacies by another.

That could include treating coral like live plants under CITES regulations, allowing corals to be exchanged among aquaculture nurseries in different countries. Organizations could also create a kind of regional genetic bank, where coral from different countries could be kept alive in tanks, or their sperm could be frozen for future use.

There’s no time to waste, warn the scientists. Coral aren’t adapting fast enough on their own. And “windows of opportunity for effective large-scale implementation of AGF are closing rapidly,” they write in the new paper. “Waiting until genetic rescue is ‘needed’ to save coral species on the brink of extinction may well be too late.”

It remains to be seen if it’s too late for Florida’s elkhorn coral.

Baker, et. al. “Proactive assisted gene flow for Caribbean corals in an era of rapid coral reef decline.” Science. July 24, 2025.

References

Posted in VEN - Good News on Climate Action - Blog

Leave a Comment

You must be logged in to post a comment.