The ocean has a way of giving you the impression that there are still mysteries in the world. Not abstract ones, but actual, tangible, massive secrets that, if you look at the right time, are sitting right there in the water. That’s essentially what happened in 2025 when a NOAA research team carrying out routine surveys to monitor coral reefs in the Mariana Islands discovered something no one had anticipated: the largest Porites coral colony ever found on Earth.
The hunt was not targeted. Nobody took a plane to the isolated Maug Islands in the Mariana archipelago with the intention of changing history. The group was there as part of NOAA’s National Coral Reef Monitoring Program, one of those meticulous, unglamorous scientific endeavors that seldom garner media attention. Then they discovered it somewhere in the submerged volcanic caldera off the Maug Islands. A coral cathedral. A single Porites rus colony that is about 14,500 square feet in size, more than 100 feet across at the top and wider at the base than four school buses arranged end to end. It was challenging to get the measurements themselves. Dr. Thomas Oliver, a chief scientist with NOAA’s National Coral Reef Monitoring Program, stated, “We actually couldn’t measure it due to dive safety restrictions because this coral was so big.” The scope of what they were examining can be inferred from that sentence alone.
It is helpful to sit with the number for a while in order to comprehend why this is important. Compared to the previous record-holding Porites coral discovered in American Samoa in 2020, the colony is roughly 3.4 times larger. To be honest, the age estimate is astounding. The team had to rely on growth rate estimates, or about one centimeter of outward growth annually, because Porites rus does not produce the growth rings that scientists usually use to date corals. This colony may be over 2,050 years old at that rate. This suggests that while ancient Rome was still an empire, it might have been subtly expanding in the Pacific. It’s the kind of information that seems fictitious until you give it enough thought.
The building is located in the Maug caldera, which is part of the Mariana Trench Marine National Monument, a protected area that was created in 2009 and includes hydrothermal vents, submerged volcanoes, and coral reef ecosystems. For many years, scientists have been drawn to this caldera. It is a sort of natural experiment in what coral ecosystems might look like under future climate scenarios because its carbon dioxide vents produce localized pockets of acidic ocean conditions. The vast coral colony that is flourishing a few hundred meters away is not reached by the concentrated acidic zone near the vents. The contrast between a living giant and a dead zone in the same obscure part of the Pacific is almost too obvious. Dr. Hannah Barkley, another program chief scientist, remarked, “It is amazing to see both these extremes – a resilient and thriving mega coral, and a dead zone near the carbon dioxide vents – in the same area.”
There’s a sense that the ocean is quietly correcting the dominant narrative when you watch this kind of discovery happen, even if you’re reading the scientific reports from a distance. Reef collapse and coral bleaching are legitimate news stories. However, this is also true: a single organism that has endured over two millennia, conflicts, shifting climates, and the overall chaos of geological time. It is important to acknowledge that local communities in the Maug Islands were previously aware of the coral’s existence. Indigenous knowledge frequently coexists with scientific oblivion, and this instance is no exception.
According to reports, the Advisory Council of the Mariana Trench Marine National Monument is attempting to name the coral in a way that respects its Chamorro and Carolinian ancestry. Perhaps more so than a formal scientific designation, that process seems significant. The enormous coral of the Mariana Islands is now part of the public record, regardless of the name it eventually takes. Since coral reef ecosystems contribute more than $3.4 billion to the U.S. economy alone each year, the stakes of safeguarding locations like this are anything but abstract. Future surveys’ precise findings regarding the colony’s entire extent are still unknown. However, the finding serves as a reminder that the ocean’s inventory is still incomplete.
