Citizen Scientists Uncover Massive Coral Colony on Great Barrier Reef
Volunteer researchers participating in a groundbreaking citizen science initiative have made a remarkable discovery on Australia's Great Barrier Reef. They have identified what is believed to be the largest documented coral colony ever recorded in this iconic marine ecosystem.
A Stunning Underwater Landscape
The massive coral structure spans approximately 111 meters in maximum length and covers an estimated area of 3,973 square meters, making it roughly half the size of a standard soccer field. The discovery was made as part of the Great Reef Census, a comprehensive monitoring project organized by the volunteer group Citizens of the Reef.
Experienced diver Jan Pope first spotted the unusual formation while surveying waters several hours offshore from Cairns. "It was quite glassy and I could see this very strange pattern in the water," Pope recalled. "When I jumped in the water, it became obvious to me that I'd found something I'd never seen anything like before."
Pope, who has been diving on the Great Barrier Reef for thirty-five years, described the coral formation as "a very surreal underwater landscape" that resembled "a rolling meadow."
Family Involvement and Scientific Significance
Pope's daughter, Sophie Kalkowski-Pope, who serves as marine operations coordinator at Citizens of the Reef, surveyed the site with her mother two weeks after the initial discovery. "We had no idea that something so significant was right here on our doorstep," she remarked.
The Great Reef Census project utilizes crowd-sourced images to monitor coral coverage across the vast expanse of the Great Barrier Reef. Since its inception in 2020, the organization estimates it has surveyed approximately one-quarter of the entire reef system.
Kalkowski-Pope explained that a primary objective of the project is to identify key source reefs—"hotspots of resilience" that can supply other reef areas with larvae during spawning events, potentially aiding in reef recovery and regeneration.
Scientific Context and Rarity
Dr. Tom Bridge, curator of corals at the Queensland Museum and senior lecturer at James Cook University, provided expert context about the discovery. He noted that Pavona clavus, the coral species identified, is relatively uncommon and "quite hard to find." However, "where it is found, it can form really, really ridiculously huge colonies," he added.
Bridge emphasized the increasing rarity of such large coral formations due to climate impacts. "Very large coral colonies are going to be exceedingly rare because we're finding bleaching is increasing in severity but also in frequency," he stated. For colonies that are dozens or even hundreds of years old, the chances of escaping bleaching conditions or withstanding elevated water temperatures are diminishing.
In 2024, a coral of the same species measuring just over 1,000 square meters was discovered in the waters surrounding the Solomon Islands, providing additional context for the significance of the Great Barrier Reef find.
Verification and Measurement Challenges
Scientific confirmation requires genetic testing to determine whether the Cairns coral represents a single colony—meaning all parts originated from one original polyp—or multiple colonies that settled in close proximity and merged as they grew.
"We would need over 300 individual samples from across the colony because it's so big," Kalkowski-Pope explained regarding the genetic testing requirements.
To estimate the colony's substantial dimensions, researchers employed photogrammetry, a technique that involves stitching together photographs taken from the water's surface to create a detailed three-dimensional model.
Serena Mou, a research engineer at the Queensland University of Technology Centre for Robotics, described the mapping process as "a bit of an interactive process" and noted that "the coral ended up being bigger than what Sophie initially thought."
Broader Scientific Initiatives
Bridge mentioned that the coral species, currently classified as Pavona clavus, is scheduled for reclassification as part of an ongoing overhaul of coral taxonomy. Meanwhile, another citizen science project called Map the Giants, operated by the University of Milano Bicocca, tracks giant coral colonies worldwide, highlighting the global interest in these remarkable marine organisms.
The discovery underscores the valuable contributions of citizen scientists to marine research and conservation efforts, particularly in monitoring vulnerable ecosystems like the Great Barrier Reef.
