This story is a part of the GenOcean campaign — an official Ocean Decade campaign showcasing Decade Actions, collaborating organizations and ocean leaders that focus on youth and citizen science opportunities to help anyone, anywhere be the change the ocean needs.
On January 18 and 19, 2025, over 400 observers across 36 countries witnessed one of the most extraordinary natural events: the synchronized spawning of Porites rus, a key tropical, reef-building coral. This groundbreaking citizen science initiative led by Tama no te Tairoto (Children of the Lagoon), part of the larger “Connected by the Reef – Te Firi A’au” Ocean Decade Activity, aimed to answer a fundamental question about reef connectivity: can coral species synchronize their reproduction on a global scale?
A Global Mission: Connecting Reefs Across Ocean Basins
Porites rus, a coral species found throughout the Pacific and Indian Oceans and extending to the Red Sea, has been known, since 2020, to spawn in a predictable and synchronized manner in certain regions. After this discovery and over the past three years, Tama no te Tairoto has worked diligently to track these events across 18 islands, collecting 426 observations that confirm this synchronization from French Polynesia to La Réunion Island. However, the question of whether this phenomenon extended across vast distances like the Pacific and Indian Oceans had remained unanswered—until now.
That’s where the “Connected by the Reef – Te Firi A’au” initiative comes in. The project, coordinated from Tama no te Tairoto’s home base in Tahiti, called on citizen scientists and coral enthusiasts from around the world to participate in the largest-ever global observation of this coral spawning event. The goal was clear: to determine if coral reefs are truly “connected” through the synchronized spawning of Porites rus.
Mobilizing Citizen Scientists Across 36 Countries
This ambitious event was not just about collecting data—it was about uniting a global community of coral conservationists, divers, marine biologists and concerned citizens to actively contribute to the study of one of the ocean’s most important ecosystems.
In French Polynesia, the spawning season of Porites rus typically begins in November and peaks in January and lasts until April. Based on the natural timing of the event, Tama no te Tairoto set the global observation window for January 18 and 19, 2025, allowing for time zone adjustments and maximizing participation worldwide.
Observers registered from 36 countries and territories, spanning from Costa Rica to the Red Sea, including regions like Fiji, the Maldives, Sri Lanka, Madagascar and even as far as Kenya and Egypt.
“This was the first time I had participated in an event like this even though I’m trying to look for these phenomena myself in my research internship on coral spawning,” says Jur de Bruin, Dutch coastal and marine management student based on Chumbe Island, Zanzibar. “I never realized events like these existed, but I was really excited to get involved.”
In total, the event brought together more than 400 participants, with over 100 of them based in 20 countries outside of French Polynesia. Despite the challenges of pinpointing the exact timing of the event and overcoming weather difficulties, this massive international collaboration demonstrated the power of citizen science in tracking large-scale ecological processes.
“It was so exciting to know that people hundreds of kilometers away were waiting for the same thing as I was when I swam out to our resort’s House reef in the Maldives,” says Elsa Chaucesse, marine life educator based in the Maldives. “Once I got out there, choosing which colonies to watch was the hardest part because I didn’t want to miss anything.”
Synchronization Across More Than 18,000 km
The results from the first wave of observations have already shown a fascinating discovery: the spawning of Porites rus occurred across vast distances, synchronized in a way that had never been observed before. Participants from French Polynesia reported the first sightings as early as 6:55 a.m. local time, with additional observations coming in from Mauritius, La Réunion Island, the Maldives and even as far as Chumbe Island in Tanzania, all within an hour and a half after sunrise at each location! This confirmed that Porites rus does indeed have the ability to synchronize its reproduction across great distances—exceeding 18,000 kilometers from one hemisphere to another.
However, not every observation site was successful. Areas like Palmyra Atoll, Guam and American Samoa did not report any spawning, providing valuable insights into the environmental factors that might be influencing this phenomenon.
“Not observing the coral spawning at certain sites is just as valuable as witnessing it, as it highlights the importance of understanding the local conditions that affect these coral populations,” notes Tama no te Tairoto founder, Vetea Liao.
The Power of Citizen Science in Coral Conservation
The success of this global event underscores the importance of citizen science in advancing coral conservation efforts. By engaging local communities, divers and marine enthusiasts, Tama no te Tairoto demonstrated how grassroots participation can contribute to large-scale scientific endeavors.
“My biggest takeaway from participating in ‘Connected by the Reef’ was that waking up at 6 a.m. was worth it! And, that citizen science can help understand better our oceans across the planet,” shares Chaucesse. “I am convinced that widespread citizen science programs, with the help of snorkelers and divers all over the planet, could help make big discoveries like we did with Tama no te Tairoto.”
This event also highlights the role of citizen scientists in protecting vulnerable coral species. By participating in projects like “Connected by the Reef – Te Firi A’au”, individuals play an essential role in monitoring the health and behavior of coral ecosystems, helping to uncover patterns that could inform conservation efforts worldwide.
Exploring New Frontiers: The Deep Dive Challenge
In addition to the broad-scale observations, a dedicated team of divers based in French Polynesia took on a unique challenge: to study the spawning of Porites rus at depths of 80 meters. This ambitious effort highlights the complexity of coral ecosystems and the difficulty of studying coral reproduction in deeper waters. As researchers continue to analyze the data, we may gain new insights into how different coral species spawn and reproduce in mesophotic and deep-sea environments.
What’s Next?
The data collected from the “Connected by the Reef” project will continue to be analyzed in the coming months, with more results expected as observations from all over the world are compiled. The early findings, however, are already transforming our understanding of coral behavior and the incredible ability of some species to synchronize their reproduction over vast distances.
This event has not only revealed the remarkable biological phenomenon of coral spawning but also emphasized the power of collective action in scientific discovery. Through citizen science, Tama no te Tairoto has shown that we all have a role to play in understanding and protecting our planet’s most vital ecosystems.
Get a sneak peek into the observation data as it’s being entered with the mobile application, “Tama no te tairoto,” available on GooglePlay and AppStore to track the spawning of this significant reef-building coral across the globe.
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