More than 1,000 scientific scuba dives have been completed across some of the Pacific Ocean’s remote coral reefs as researchers begin the lengthy process of determining how these ecosystems are changing.
Scientists working with NOAA Fisheries completed 1,006 scuba dives during the 2026 Pacific coral reef monitoring mission, surveying sites across American Samoa and the Pacific Islands Heritage Marine National Monument.
The expedition took researchers from Hawaiʻi to Jarvis Island, Palmyra Atoll and Kingman Reef before a roughly 2,000-kilometre transit to American Samoa. There, teams worked around Tutuila, Ofu, Olosega, Taʻū, Swains Island and Rose Atoll. Howland and Baker Islands were surveyed during the return journey.
For divers, the scale of the underwater work is striking.
More Than 1,000 Scientific Dives
Rather than relying on observations made solely from ships or remote sensing, scuba divers were fundamental to the mission.
According to NOAA Fisheries, researchers completed 1,006 dives while assessing coral reef health and surrounding ocean conditions.
Those dives contributed to 440 fish surveys and 420 photomosaic surveys, with scientists capturing thousands of underwater images that will eventually be assembled into detailed 3D models of sections of reef.
Researchers also carried out 550 photoquadrat benthic surveys and 21 carbonate budget surveys.
The work allows scientists to return repeatedly to reefs and compare changes through time rather than relying on isolated snapshots of reef condition.
Building 3D Records Of The Reef
One of the more visually striking parts of the project involves divers photographing large areas of reef.
Thousands of overlapping photographs can be combined through photogrammetry to construct three-dimensional representations of coral communities.
These models provide researchers with a permanent digital record that can be analysed and compared with future surveys.
The diving programme was only one part of the expedition.
Scientists collected 261 water samples, deployed 110 temperature recorders and worked with instruments designed to measure processes including reef calcification and bioerosion.
At night, attention shifted away from the reef itself. Researchers conducted 139 sampling tows looking for juvenile fish and fish larvae in the surrounding pelagic environment.
Repeated Surveys Across The Pacific
The expedition forms part of NOAA’s National Coral Reef Monitoring Program, which tracks reef ecosystems throughout US waters.
The 2026 expedition marked the tenth monitoring survey in American Samoa since 2002 and the sixteenth in the Pacific Islands Heritage Marine National Monument since 2000.
Researchers aim to revisit these particular islands approximately every three years.
That repetition matters.
Coral reefs face pressures ranging from warming seas and ocean acidification to disease and land-based pollution. Long-term monitoring gives scientists a way of distinguishing short-term fluctuations from more persistent changes.
The programme also examines reef fish populations. Divers identify, count and estimate the size of fish without removing them from the ecosystem.
Now The Analysis Begins
Completing the dives does not mean scientists already know what the expedition has revealed.
The substantial body of information gathered during the mission must now be processed and compared with previous surveys.
NOAA says researchers will combine information from temperature loggers, fish surveys, coral surveys and other monitoring equipment to examine what has happened across these Pacific reefs during recent years.
Summary data from the expedition are expected to become available in approximately a year.
That analysis could ultimately provide a much clearer picture of how some of the Pacific’s remote coral ecosystems are responding to changing ocean conditions.
For now, however, the achievement is also a reminder of how much traditional underwater fieldwork remains behind modern marine science.
More than a thousand dives, hundreds of reef surveys and millions of potential data points later, the expedition is over.
The work of understanding what those reefs are telling us has only just begun.
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