A remarkable feat of international collaboration is revealing new insights into the reproductive habits of coral reefs. Originating with a local initiative in French Polynesia, the association Tama no te Tairoto, Les Enfants du lagon, has spearheaded a decade-long study documenting the synchronized spawning of Porites rus coral across vast distances – a phenomenon recently recognized by the United Nations as a key action within the Decade of Ocean Science. New research, published in Global Ecology and Biogeography, confirms this intricate biological coordination, offering critical data as reefs worldwide face increasing threats from climate change.
© Felix Gouniot / Captain Darwin
A local initiative originating in the Polynesian lagoons has captured the attention of the global scientific community. Over several years, the association Tama no te Tairoto, Les Enfants du Lagon, has transformed a natural observation into a large-scale international research program, revealing one of the most fascinating and precise biological phenomena in the tropical ocean.
Synchronized Coral Reproduction Observed Across Vast Distances
In January 2025, Tama no te Tairoto will coordinate the largest participatory observation campaign ever conducted on the spawning of Porites rus coral. The project, named Connected by the Reef Te Firi A’au, mobilizes an unprecedented network of divers, scientists, teachers, and citizens, with support from IFRECOR, the ICRI, and is registered within the United Nations Decade of Ocean Science. The resulting underwater imagery has surprised even seasoned observers. A whitish cloud engulfs the water – not fog, but millions of reproductive cells released simultaneously by coral colonies, marking the beginning of larval dispersion and the formation of new reefs.
The event took on historical dimensions when Porites rus spawning was observed on the same day, at the same time, in two different oceans. From the Pacific to the Indian Ocean, from Polynesia to Tanzania, and extending to the Maldives and Réunion, the phenomenon was recorded across more than 18,000 km and both hemispheres. More than 400 observers, spread across 20 countries, transmitted their data in real-time using a mobile application developed by the association.
A Biological Clock Tuned to the Moon and Sun
The collected data reveals remarkable precision. Spawning occurs five days after the full moon and approximately 1 hour and 30 minutes after sunrise, between November and April, with peak intensity in December and January. On January 18, 2025, the synchronization was striking. In Tahiti, spawning was recorded 1 hour and 22 minutes after sunrise. At Chumbe Island, Tanzania, it occurred 1 hour and 23 minutes after sunrise – a difference of just one minute, confirmed by consistent observations in New Caledonia, Mauritius, Indonesia, and the Maldives. This level of coordination challenges existing understandings of coral reproduction.
As early as 2022, marine biologist James Guest, a reef specialist at the University of Newcastle, highlighted the unprecedented scale of the initiative, calling it one of the most important citizen science projects ever dedicated to corals.
© Alice Carpentier
Major Scientific Recognition
2025 marks a decisive step with the publication of the first scientific article dedicated to this large-scale, synchronized daytime spawning event. Titled “Shining a Light on Daytime Coral Spawning Synchrony Across Oceans,” the study appears in the international journal Global Ecology and Biogeography published by Wiley. It is led by Charlotte Moritz of CMOANA Consulting and ten co-authors from research, the non-profit sector, and the Polynesian scientific community.
Based on ten years of observations, between 2014 and 2023, covering 104 reefs across 15 islands, the study highlights a common biological clock in Porites rus across two oceans. It demonstrates the combined influence of water temperature, depth, and light on seasonal variations in spawning time. Such synchrony has never before been documented at this vast spatial scale in corals. This research validates the observation protocol painstakingly built by Tama no te Tairoto and recognizes the crucial contribution of over 300 volunteer observers. It also opens new avenues for research, particularly on the impact of climate change on biological synchronization mechanisms.
Porites rus: A Resilient Reef Builder
Widely distributed throughout the Indo-Pacific region and the Red Sea, Porites rus plays a structuring role in tropical reefs. Capable of adopting branching, massive, plate-like, or encrusting forms depending on its environment, it can live from the surface to depths of 80 meters. At greater depths, it spreads into plateaus to capture light, sometimes forming monumental structures that harbor exceptional reef biodiversity. This species’ resilience is particularly noteworthy, as it appears less sensitive than others to temperature variations, turbidity, or certain bleaching events. This makes Porites rus a key species for understanding the future of reefs in a changing ocean.
© Vetea Liao
Observe to Understand, Understand to Protect
Since the first observation of the phenomenon in 2014, marine biologist and Tama n? te Tairoto co-founder Vetea Liao has relied on an ever-expanding network of volunteers. In Polynesia, teachers, divers, and students now participate in observations, particularly within marine educational areas supported by the National Education system and the French Biodiversity Agency. Witnessing a reef reproduce changes perspectives on these ecosystems, with many realizing that corals are complex living organisms, not simply mineral structures. This awareness extends beyond the general public, with professionals in the maritime sector now seeking the association’s input to adjust their work schedules and minimize disruption during reproductive periods.
Citizen science is thus becoming a concrete lever for transforming practices, creating a direct link between observation, knowledge, and protection. The findings underscore the potential of collaborative research to drive conservation efforts.
An App to Connect Reefs and People
The development of the Tama no te Tairoto mobile application has been key to the project’s success. Designed for fieldwork, it allows for the collection, geolocation, and instant sharing of data on coral reproduction and other marine species. It now unites hundreds of observers, professionals and amateurs alike, around a common goal.
Building on this momentum, the association now aims to further expand its network. Given that Porites rus is present in over 50 countries and territories between the Pacific, Indian Ocean, and Red Sea, the challenge is to multiply observations to refine the understanding of the mechanisms regulating this planetary synchronization.
Success Recognized by the United Nations
In June 2025, Tama no te Tairoto was invited to the third United Nations Conference on the Ocean in Nice. The association presented the immersive exhibition “Les récifs du temps” (The Reefs of Time) and the clip “Moana to’u ora,” created with students from the Punaauia college. This emblematic project brings together science, Polynesian culture, and youth engagement. Having received the TO’A REEF 2024 trophy from IFRECOR and been recognized by the United Nations as an official action of the Decade for Ocean Science, Tama no te Tairoto today embodies a rare model – one of open science, rooted in territories, capable of connecting people through reefs, and emerging from a Polynesian lagoon to provide a global understanding of life.
