Once a year, typically after sunset in the late summer, the coral baby-making process begins.Large colonies of coral spawn, spewing out sperm and eggs, often in pea-size bundles, that drift around until they encounter the spawn of other corals. Fertilized eggs turn into coral larvae — tiny and squishy free-swimming organisms — which eventually settle on the seafloor. There they metamorphose, like a caterpillar to a butterfly, into a coral polyp. Those polyps clone themselves over and over again, eventually forming larger coral colonies that build reefs.That’s how typical reef-building corals, like the iconic elkhorn and staghorn species, with their antler-like appearance, produce offspring. That’s how they’ve been doing it for millions of years.But in Florida, this process is broken.Most species of hard corals that form the reef’s complex structure and help safeguard coastal communities from storm surge are not having babies in the wild anymore, top marine ecologists told me. For at least a decade, and likely longer, researchers have barely found any new coral babies or juveniles of most hard corals during surveys in South Florida and the Florida Keys, home to the largest coral reef in the continental US. “We’re just not seeing new babies,” said Scott Winters, CEO of Coral Restoration Foundation, a conservation group.While many of these corals are still spawning in the wild — the part where they release sperm and eggs — something is preventing that spawn from eventually growing into polyps, or babies, Winters, and other experts said.An elkhorn coral in the Florida Keys that bleached during the 2023 marine heat wave.Jennifer AdlerThis is a serious problem for a long embattled reef. Florida’s reef ecosystem has been facing a near-constant barrage of disturbances, from marine heatwaves and hurricanes to disease and pollution. These threats have killed off most of the live hard coral in the Florida Keys. And should the reef’s reproductive woes persist, it may never recover or even survive on its own. While corals can reproduce asexually — by cloning themselves — sexual reproduction is incredibly important because it introduces new genetic diversity that helps corals adapt to the increasingly hostile ocean conditions.RelatedNow, to keep Florida’s reef alive, scientists have to breed corals almost entirely in labs on land, where the water is clean and comfortably warm. Margaret Miller, a coral reproductive biologist, says it’s a sign that reef conservation is in a new era — one in which saving corals requires managing them under human care.Why aren’t corals making babies?“We just don’t know,” Winters said.There’s no one explanation for the baby bust, marine scientists told me. Rather, each step of the reproductive process has likely been compromised to some degree.Over the last few decades, coral reefs in Florida and across much of the Caribbean have lost an enormous amount of their large, adult coral colon
Mar. Feb 4th, 2025
