NOAA Expedition Studies Mesophotic Coral Reefs in the 'Au'au Channel

CRED scientist John Rooney conducts a mesophotic video transect. NOAA photo by Ray Boland.
CRED scientist John Rooney conducts a mesophotic video transect. NOAA photo by Ray Boland.

On July 7, 2010, 11 scientists from PIFSC, the University of Hawaii and Bishop Museum departed Pearl Harbor for an 11-day cruise aboard the NOAA Ship Oscar Elton Sette. Chief scientist for the expedition was researcher John Rooney from the PIFSC Coral Reef Ecosystem Division.

The cruise mission was to study a series of coral reefs in the Au'au Channel between the islands of Maui and Lana'i in the main Hawaiian Islands. The reefs there feature luxuriant expanses of stony, or scleractinian, corals as well as macroalgae, reef fishes, and other coral reef organisms. Most reefs in Hawai'i are found at depths of about 100 ft or less and are most prolific at depths of around 40 ft. The reefs studied in the Au'au Channel are unique in that they are most prolific at a depth of about 280 ft and have been found to flourish even below 400 ft.

The expedition involved several types of scientific operations. Several mixed-gas scuba dives were conducted to identify fish associated with the reefs, estimate their abundance and size composition, and collect high-definition video of the seafloor along survey transects. The video data will be analyzed to assess the species and size composition of corals. An underwater camera sled was deployed at night to better characterize the distribution of mesophotic reefs. In addition, acoustic surveys (using sonar) were conducted to learn about communities of small fishes, squids, and other organisms that typically live offshore but may also contribute nutrients to the mesophotic reefs of the 'Au'au Channel.

Previously deployed oceanographic instruments that record information about currents, ocean temperatures, and the passage of tagged fishes were recovered during the cruise so the collected data could be downloaded for analysis.

For more information about this cruise and mesophotic coral reefs, go to