Vanuatu’s fluorescent corals could face another major challenge as scientists look ahead to a potential marine heatwave in early 2027.

Fluorescent corals may look like ordinary brown or green corals in daylight, but under a special blue-light torch at night, they glow in striking colours, including blue, green and red.

Senior coral scientist with Reefs of Hope, Dr. Anya Salih who has been studying corals globally for a decade now, says Vanuatu has a high diversity of these corals, whose fluorescent pigments help protect them from damaging light and make them more resilient to heat stress.

She says her observations around Vanuatu have revealed a high number of fluorescent corals.

These corals contain special pigments that help manage sunlight and protect the microscopic algae living inside their tissues.

But while these protective mechanisms may improve their chances of survival, Dr. Salih still do not know how well Vanuatu’s fluorescent corals will withstand the coming heatwave.

“The question is now, with the coming heat wave in 2027, which is predicted to be maybe February, March, April, we don’t know when and we don’t know how bad it’s going to get. We just know that the prediction is that this El Niño event is going to be the most severe event in human recorded history. So, the question will be what happens to the reefs here,” Dr. Salih said.

Corals may look like plants, but they are marine animals that depend heavily on microscopic algae living inside their tissues for food.

Dr. Salih explains that when ocean temperatures become too high, the protective mechanisms within corals can break down.

The corals then expel the algae that provide much of their food, causing them to turn white in a process known as coral bleaching.

Dr. Salih said while corals can recover from short periods of bleaching, prolonged exposure to heat stress can eventually kill them.

“But when the upper limits of temperature are exceeded by even two degrees, then those mechanisms that the corals have to protect themselves from toxic molecules, from the algae in their skins, they break down and they expel the algae and turn white. And this is called coral bleaching.

And if coral bleaching happens for a short duration, corals usually recover. But when it goes on for weeks and weeks and months, then corals can die.”

However, not all corals respond to environmental stress in the same way.

Dr. Salih says fluorescent corals have protective pigments that help manage potentially damaging light, making them better able to handle strong sunlight and, in some circumstances, heat stress.

During her observations around Efate, Tanna and Aore, she found many fluorescent corals across local reefs.

But she warns that their ability to withstand rising temperatures is limited.

“And when we compare the fluorescent corals to non-fluorescent corals, the fluorescent corals are better able to handle strong sunlight, and they’re better at surviving heating, heat waves. And what I’m finding in Vanuatu is that Vanuatu reefs are very fluorescent.

There’s a lot of fluorescent corals. What we don’t know is how resilient these corals are to heating. Of course, as temperature heat waves get worse and worse, even the resilience of resilient corals will be exceeded,” said Dr. Salih.

With the severity of the next heatwave and its impact on Vanuatu still uncertain, scientists are working to give vulnerable reefs a better chance of survival.

Through partnerships with local resorts and local organisations such as the Vanuatu Climate Action Network (VCAN), Reefs of Hope is supporting coral restoration projects, including plans to establish nurseries around Efate and Santo.

The approach involves selecting corals already adapted to higher temperatures, moving them into cooler nursery areas and monitoring which ones survive.

The aim is to allow these corals to grow and reproduce, producing larvae that could help repopulate damaged reefs.

To improve the chances of coral survival, scientists are developing a special dome-shaped structure to support coral restoration.

Unlike corals growing on a flat surface, the dome allows scientists to attach several types of coral in one structure and move them into deeper, cooler water.

The team selects corals that have already adapted to higher temperatures in shallow waters, with the aim of helping them survive future heatwaves, reproduce and eventually repopulate damaged reefs.

“What we’re trying to do is take corals that are already more resilient to high temperature. So we select corals that are growing in very hot, very shallow areas that at low tide, they might be almost exposed.

And when it becomes too much, they will bleach. But if we take some of these corals and put them on these specialized metal domes that you saw yesterday, and we move them into deeper water, and if that water is cooler by some two degrees, then when heating happens, those corals we hope will survive because they’re already adapted to a higher temperature in the shallow parts,” said Dr. Salih.

She says the restoration work is intended to “buy time” for reefs by helping more resilient corals survive and reproduce.

However, she stresses that coral nurseries alone cannot solve the global coral reef crisis.

She said reducing dependence on fossil fuels and cutting greenhouse gas emissions remain essential to slowing the ocean warming that drives mass bleaching events.

“The only solution for coral bleaching is to reduce fossil fuel reliance and emissions. It’s the only thing that will stop, reduce the bleaching.

And what we’re trying to do is buy time, because if the temperatures are going up very, very fast, there is no hope for coral reefs worldwide.”

For Vanuatu, the challenge is now to understand which coral varieties can withstand future warming and how restoration efforts can help protect the country’s reefs.

Although fluorescent corals offer hope because of their greater tolerance to sunlight and heat stress, scientists warn they cannot withstand unlimited warming.

As the region looks towards early 2027, the survival of Vanuatu’s coral reefs may depend on both identifying the corals most capable of adapting and addressing the wider causes of ocean warming.

Reefs of Hope is a coral science and restoration initiative focused on helping coral reefs adapt to climate change and survive rising ocean temperatures.