A mother-and-daughter team of citizen scientists has identified a significant coral colony on Australia's Great Barrier Reef, which is believed to be the largest documented single coral structure globally.
The Pavona clavus colony measures approximately 111 meters in length and covers an estimated 3,973 square meters, prompting further scientific inquiry into its size, age, and implications for coral resilience.
Discovery and Initial Identification
The discovery was made late last year by Jan Pope, an experienced diver, and her daughter Sophie Kalkowski-Pope, a marine operations coordinator. They were participating in the Great Reef Census, a citizen science initiative managed by Citizens of the Reef, a conservation organization. The coral was found in waters several hours offshore from Cairns, Far North Queensland.
Scale and Global Context
The Pavona clavus colony spans approximately 111 meters (364 feet) and covers an area of around 3,973 square meters (42,765 square feet), an area roughly half the size of a soccer field. Citizens of the Reef reported that the structure is among the largest documented and mapped coral colonies globally.
Previous recorded contenders for large coral structures include a 34-meter colony off the Solomon Islands and a 71-meter colony in Nusa Penida. Experts note that global records for corals exceeding 100 meters in length are currently absent.
Verification and Scientific Methodology
Following the initial find, Sophie Kalkowski-Pope returned in January with Citizens of the Reef to conduct detailed mapping and measurement. The size was verified using manual underwater measurements, high-resolution imagery captured from the water surface, drones, and measuring tapes.
This data was then used to create a 3D model of the coral through photogrammetry, a technique that stitches together photographs. Research engineer Serena Mou confirmed the coral's size exceeded initial estimates.
Scientific Context and Hypotheses
The Australian Institute of Marine Science (AIMS) research scientist Mike Emslie estimated the colony's age to be at least several hundred years. Dr. Tom Bridge, curator of corals at the Queensland Museum, noted that Pavona clavus is an uncommon species but capable of forming exceptionally large colonies. He also observed that very large coral colonies are becoming increasingly rare due to the escalating severity and frequency of coral bleaching events worldwide.
Scientists are examining whether strong tidal currents and low exposure to tropical cyclone waves at the site, compared to other parts of the Great Barrier Reef, may have contributed to the coral's large structure and prolonged undiscovery. The area has been described as "tidally dominated," which can present difficult diving conditions.
To definitively confirm the structure as a single colony originating from one polyp, genetic testing would be required, potentially involving over 300 individual samples. An alternative possibility is that the coral comprises multiple colonies that settled closely and coalesced over time. The species Pavona clavus is also scheduled for reclassification as part of an upcoming revision of coral taxonomy.
Implications for Resilience and Management
The presence of such large, long-standing corals suggests resilience against repeated disturbances, including mass coral bleaching, cyclones, and crown-of-thorns starfish outbreaks. James Cook University marine scientist Allison Paley suggested that while this colony was likely undiscovered, other equally large corals might exist globally but remain unrecorded.
The specific location of the coral has not been publicly disclosed to minimize potential impacts. It will be monitored and managed by the Great Barrier Reef Marine Park Authority.
Role of Citizen Science
The discovery highlights the role of citizen science initiatives. The Great Reef Census, run by Citizens of the Reef, involves over 100 vessels and citizen scientists in collecting reef imagery. Since 2020, the organization estimates it has surveyed a quarter of the reef.
A key objective of the project is to identify "hotspots of resilience" or source reefs that can provide larvae to other reefs during spawning events, complementing existing monitoring programs. This discovery occurs amidst a global bleaching event that began in 2023, affecting over 80% of the ocean's reefs.