Massive 2,000-Year-Old Megacoral Discovered in Mariana Islands Volcanic Crater Offers Clues to Reef Resilience

NOAA scientists have discovered a massive coral colony in the Maug caldera that may be over 2,000 years old and holds secrets to surviving ocean acidification.

By: AXL Media

Published: Apr 30, 2026, 11:05 AM EDT

Source: Information for this report was sourced from EcoNews

A Record-Breaking Discovery in the Depths of the Maug Caldera

Scientists with the National Oceanic and Atmospheric Administration (NOAA) have recently documented a monumental coral formation in the Mariana Islands that challenges previous records for reef growth. Formed by colonies of Porites rus, the "megacoral" sits within the submerged crater of an ancient volcano, measuring nearly 200 feet wide at its base and rising over 100 feet toward the surface. Covering an area roughly equivalent to three professional basketball courts, the structure is more than three times larger than the previous record-holder in American Samoa. Chief scientist Thomas Oliver noted that the sheer scale of the coral presented significant logistical hurdles, as its massive dimensions made it difficult to measure under standard dive safety protocols.

Estimating Two Millennia of Marine Persistence

Determining the precise age of the Maug coral is a complex task because the Porites species does not produce the distinct annual growth bands found in other reef builders. Instead, NOAA researchers rely on radial growth estimates of approximately four-tenths of an inch per year to calculate the colony's longevity. These preliminary assessments suggest the coral has been growing for more than 2,050 years, making it a witness to twenty centuries of changing ocean chemistry. This ancient survivor acts as a biological archive, potentially holding information about historic environmental shifts that occurred long before modern industrial activity began altering the global climate.

Thriving in a Natural Laboratory of Acidic Seawater

The most intriguing aspect of the discovery is the coral’s proximity to active hydrothermal vents that release high concentrations of carbon dioxide into the surrounding water. This volcanic activity creates a "champagne-like" environment where the seawater is naturally more acidic than the open ocean. Chief scientist Hannah Barkley emphasized the remarkable contrast between the thriving megacoral and the nearby "dead zones" located immediately adjacent to the vents. This setting provides a rare, real-world preview of the future conditions coral reefs may face as the world's oceans continue to absorb atmospheric CO2, offering a glimpse into which species might possess the resilience to survive.