Coral reefs may only cover a tiny fraction of the ocean floor, but they are home to about a quarter of all marine species. However, many are dying from warming oceans and pollution. In this episode, Ocean takes a look at what has been done not only to preserve the reefs, but to bring them back to life.
Bonaire is a Dutch island in the Caribbean Sea famous for its extraordinarily rich coral reef. A true wonder of the ocean, the reefs provide income and food to hundreds of thousands of people. They too capture carbon dioxide and protect tropical shores from storms. Bonaire designated its coastal waters a national marine park in 1979. All maritime activity is strictly regulated by rangers who patrol to enforce the rules.
âEverything from the high water mark to 60 meters deep is Bonaire National Marine Park. We have one of the best protected reefs in the Caribbean region. Wherever you go in the water, you are guaranteed to see incredible biodiversity, âsays Roxanne -Liana Francisca, marine and wildlife biologist at STINAPA Bonaire.
“We have already lost nearly half of our reefs”
Rangers use sensors to check the water temperature at different depths: warming can cause bleaching, either bleaching the coral or killing it in some cases. Sewage or ingredients in sunscreen are also a threat, as does overfishing, which can lead to the spread of harmful algae and worms. For these reasons, biologists monitor reefs for signs of damage.
âPeople have looked at our reefs in one way or another for 40 years. Even though our reefs are still in fairly good condition, we have already lost almost half of our reefs, if we look at the depths of 5 and 10 meters. . Last year we had a really big bleaching episode where about 60% of our reefs had some degree of bleaching. Lucky for us, most of the corals have recovered, âFrancisca said.
The health of the reef is deeply linked to Bonaire’s interior ecosystem – with its rich wetlands, mangroves and bird habitats. Over the past decade, Bonaire’s population has doubled. This has led to increasing amounts of waste and pollution – for example deforestation – ending up in the ocean. Such threats to coral are not unique to Bonaire.
Vital for the planet and the economy
Each year, the reefs of the Caribbean generate hundreds of millions of euros in revenue for the tourism sector. Bonaire, which calls itself “a diver’s paradise”, is a magnet for divers and snorkelers all year round.
A number of local dive centers support “Reef Renewal Bonaire” – a small non-profit organization led by Italian marine and environmental researcher Francesca Virdis. Ten years ago, she created the foundation with the aim of saving the island’s endangered reefs.
A shallow area we visit was a thriving reef just a few decades ago. Now it is covered with debris of dead corals.
âUnfortunately coral reefs are dying all over the world. And although in Bonaire we can still say that we have somehow one of the best reefs in the Caribbean, it is not as pristine as it used to be,â explains Francesca.
One way to give the coral a fighting chance is in something called “coral gardening”: around 15,000 corals of several different species are grown in local underwater nurseries. Reproduction is encouraged by cutting the coral in half – a technique known as fragmentation.
âYou know, corals, actually, are colonies of thousands of little polyps, and they can divide and form new polyps. So let’s say I’m a coral and I cut off a piece of my arm. grow up another Francesca, and Francesca will be able to develop another arm, so we will have two Francescas. “
“Reef Renewal Bonaire” has only a few staff members. The non-profit organization relies mainly on private donations and volunteer support, although some of its projects receive public funding, notably from the EU.
âWe are replanting over seven thousand five hundred pieces of coral this year at the 10 restoration sites that we have … On every tree, in every nursery that we have here, all the corals are of the same genotype. And that way when they are put together or when they touch each other, they grow together and merge, âsays Ernst Noyons, restoration technician at Reef Renewal.
However, genetic similarities within the coral can make the reef vulnerable. A new restoration technique can eliminate this by using the coral’s reproductive cells instead of breaking them up.
âWe use the sexual reproduction of corals to produce new genetically unique individuals. And that’s very important because the higher the genetic diversity on the reef, the more resilient the reef itself,â explains Francesca.
Coral releases reproductive cells into the water in what is called âmassive spawningâ. Researchers collect them, fertilize them in the laboratory, to produce larvae which then settle on star-shaped ceramic plates that are placed in floating pools at sea.
âWe make sure that a lot of larvae settle on those stars, then we bring the stars back, by the thousands, and we replant them on the reef – then we monitor the growth of the small establishment on it,â explains Virdis.
Klein Bonaire is a small, protected island off the west coast of Bonaire and is home to a vast reef of staghorn corals. Covering two thousand square meters, this is just one of Reef Renewal’s many plantations. The team emphasizes that everyone can play their part, whether it’s using eco-friendly sunscreens, making a donation, or even volunteering for coral restoration themselves. Divers can take a two-day training course to learn the basics of maintaining a coral nursery.
âAlmost 80% of the dive shops on Bonaire – they are now part of the program, and the people are great, super enthusiastic,â says Guillermo Alcorta, Reef Renewal dive instructor.
A Belgian marine biologist participating in the training tells us: âI think reef preservation projects are vitally important! I really wanted to learn more in depth so that I could play a role.
Another marine biologist from the UK, who also takes part in the training, says: âSometimes it feels like a long way away, it’s underwater – how can you help? But it gives people a practical opportunity to make a difference. ”
This passionate work can make a huge difference in the preservation of local reefs. But the long-term survival of the coral will depend on our ability to reverse global warming and remove other threats to marine life in the decades to come.