Reefs are in trouble. Can scientists nurture more resilient coral?

Soon after sunset one evening in August, a few days after the late-summer full moon, the coral species Acropora cervicornis decides it is time to breed. 

During an approximately 140-minute window, this coral – commonly known as staghorn in a reference to its branchy, antler-shaped structure – releases a snow globe display of gametes into the water: packages of egg and sperm that ride the ocean’s currents toward nearby but genetically distinct reefs. There, they will meet other staghorn gametes that have also spawned, coordinating somehow across a watery expanse with guidance from the moon, the currents, and each other.

In a best-case scenario for the coral, these mixing gametes will fertilize, exchanging the sort of genetics that allow for resilience in what has always been a changing ocean world. They will develop in the water for a number of days, then the larvae will sink and settle on clear patches of reef substrate – the real estate available for coral babies – where they will grow and live for the rest of their lives, forming a key part of the ecosystem that protects and supports coastal communities worldwide. 

But for coral these days, it is far from a best-case scenario. 

Over the past decades, humans have disrupted this finely tuned dance of coral procreation. Because of damage from both climate change-charged storms and climate change-accelerated die-offs, reefs are often so far apart that wandering gametes simply never float into mates. The substrate is also more likely to be covered with seaweed thanks to changing water temperatures and pollutants, which leaves fewer places for coral to settle. And those baby corals that do find homes are increasingly stressed by warming ocean waters. 

Which is why Natalia Hurtado, lead scientist with the Bahamas Coral Innovation Hub on the southern