The divers observe the coral frai in French Polynesia.
I plunged at the back of our sailboat in the warm waters of the South Pacific just after sunrise. My 10-year-old husband and son followed, each holding an underwater camera. Together, we started on a neighboring coral reef.
It was not the first time that apnea diving off the magnificent island of Taha’a in French Polynesia. My family had already spent two weeks to explore the islands of society abroad a catamaran that we had chartered Dream Yacht around the world.
But was Our first plunged apnea as scientific citizens. Our task: Document if the coral below has sent a cloud of eggs and sperm. This is called the broadcasting frai, and that’s how Corals have sex To reproduce and create reefs.
We extend, hovering at the top of mounds of coral teeming with colored fish. Then we waited to see if the reef has released its belongings.
We were not the only ones in apnea that morning looking for eggs and sperm. On January 18, more than 400 observers from 20 countries volunteered to watch Coral Spawn. The divers were spread over 11,000 miles from the Pacific, covering the two hemispheres, from Polynesia to Tanzania. Our combined observations help to follow the health of coral reefs through half of the world.
More than 500 scientific citizens have documented corals in the world.
“Corail laying is the only way for a reef to be resilient. You get a new generation of corals, and this new generation can adapt to its new environment, “explains Vetea Liao, a marine biologist based in French Polynesia who organized the very first global observation event called connected by the reef.
This scientific effort of the citizens of the world has focused on an important kind of creation of coral reefs called Rus porites. This is the only kind of known coral Reproduce in daylight instead of the night.
It also appears as a clockwork: five days after the full moon, 90 minutes after sunrise during the hot season.
Liao discovered this phenomenon in November 2014 while fishing at his house in Tahiti. “I was really surprised. I didn’t know that Coral could appear during the day, ”he says.
The only kind of coral known to reproduce in daylight
No one else did either. Liao found no scientific study on the Corail Frai in sunlight rather than night. He therefore organized friends around French Polynesia to help him look at the reef to confirm the phenomenon. In November 2019, they documented Rus porites Posser around several islands at the same time.
But as most coral species only reveal once a year, Liao assumed Rus porites was also an annual reproach. Then a friend told him that “water was very cloudy” in December also. Liao has discovered that this type of coral is reproduced much more frequently than other species.
In 2021, Liao founded the non -profit association Tama no te tairoto (Children of the Lagon) To engage more people in the collection of data on the Coral Frai. The global observation event in January 2025 required a lot of planning and coordination, in particular the awareness of the media, the development of a new application for volunteers to record their data and the creation of an international diver network who knew what to look for.
My family learned the event of an article in the magazine in Air Tahiti flight. As Comes from passionate divers and students from the world of two childrenMy husband and I set aside the date and time of our calendars. What better way to promote future ocean goalkeepers than to involve children to collect useful information about its inhabitants?
The author and his son relax after the diving near Taha’a to observe the Frai des Coraux.
At 7:32 am, I saw white ladies to emerge from the reef below me. Excited, I agitated my son and my husband. We have turned in turn to take photos, moving between the reefs when they have pumped millions of larvae that spread to the ocean to create new reefs that support all kinds of underwater creatures.
“There is a genetic superhony of information on the corals that cross the oceans that we have no idea until we were really studying these things,” explains Peter Molnar, co-founder of the Ocean Genomic Atlas Project which aims to identify, sequence and catalog the millions of tiny plankton swimmers in our seas, including coral larvae.
We have returned to our sailboat to record our observations and download photos in the mobile application, happy that our hobby has contributed to other efforts to understand the seas.
What triggers synchronous coral sex?
A few weeks later, Liao sent an email to volunteers an initial summary of the results. The Frai has been confirmed in more than a dozen countries. For the first time, documented observers Rus porites Posser simultaneously in the southern hemisphere and in the northern hemisphere. Another fascinating discovery of the global observation event was that the FRAI was delayed by four hours for Rus porites Colonies observed at depths of 40 m and less.
In some countries, observers do not have Document Le Frai, as in the Cook Islands, Guam and the Philippines. Other regions, such as Maldives and Tanzania, had a mixture of results, with certain sites generated and others not. This could mean that not all coral colonies reproduce in the same month, or that local environmental factors influence the Frai, such as the presence of fresh water after recent rain.
The big question to answer then: what triggers this synchronous coral sex? The hypotheses range from wind or atmospheric pressure to water chemistry or at the time of the sun. Once we know what gives the green light so that the coral can reproduce, we can better target the means of Protect this important marine resource.
“It is really a great scientific mystery,” explains Liao, who, the voluntary divers, help to fell throughout the world. “The science of citizens is very powerful. You can have many eyes in the water at the same time. It is a very rapid way to obtain concrete actions towards the protection of coral reefs. ”