Uncovered: The hidden world of Hawaii’s ‘Twilight Zone’

A 20-year study exploring Hawaii’s remarkable mesophotic coral reefs, conducted and co-authored by over 16 scientists from Bishop Museum, NOAA, University of Hawaii, and state agencies was published on October 4th in the open-access journal PeerJ.  For a link to the full publication on Hawaii’s mesophotic coral reefs:


Some of the findings include the discovery of the largest uninterrupted mesophotic coral ecosystem ever recorded, with 100% coral cover and the highest rates of endemism noted anywhere on earth for reef fish!

The mesophotic zone is a depth range between 100 and 500 feet.  Meso means ‘middle’ and photic means ‘light’, so it’s no surprise that the term ‘twilight zone’ was coined for this area where light can barely penetrate.

The largest challenge for exploring mesophotic coral ecosystems is the depth.  Scuba divers can just barely reach those depths and are limited by the amount of time they can spend on the bottom before having to start returning to the surface (usually less than 20 minutes).   Submersibles can stay down for hours but are limited by their small motorized arms and lack of dexterity.

To overcome these challenges, the research group combined strategies.  The submersibles stay underwater for extended periods exploring these uncharted areas and scouting locations suitable for the experiments, and then the divers join them to conduct experiments and collect specimens.

Dr. Richard Pyle, lead researcher on the project and a zoologist at the Bishop Museum explains, “Submersibles can go much deeper and stay much longer, but divers can perform more complex tasks.”

Without the combined efforts of multiple researchers from multiple institutions using multiple underwater technologies, it would have been impossible to complete the research.

Win one for ultimate collaborations!

To learn more about the discoveries made about Hawaii’s twilight zone:




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