Coral Reef Ecosystem Monitored in the Hawaiian Archipelago; Coral Bleaching Observed at Kure Atoll

Galapagos sharks near Kure Atoll. NOAA Photo by Mark Manuel.
Galapagos sharks near Kure Atoll. NOAA Photo by Mark Manuel.

Over the past several months, coral reef scientists at PIFSC and their research colleagues completed surveys to systematically monitor and assess coral reef ecosystems across the Hawaiian Archipelago. In September 2010, staff in the Center's Coral Reef Ecosystem Division (CRED) and other scientists boarded the NOAA Ship Hi'ialakai for a 26-day Pacific Reef Assessment and Monitoring Program (Pacific RAMP) cruise in the Northwestern Hawaiian Islands. Collaborators included researchers from the Papahānaumokuākea Marine National Monument, the University of Hawai'i Joint Institute for Marine and Atmospheric Research, Ocean Associates, and San Diego State University. Chief Scientist for the expedition was CRED researcher Peter Vroom.

The cruise focused on French Frigate Shoals, Pearl and Hermes Atoll, Kure Atoll, and Lisianski Island. The field party used standard Pacific RAMP techniques to survey benthic fauna, fish populations and oceanographic properties and to deploy and retrieve scientific instruments. For the first time in the NWHI, CRED staff installed calcification acidification units (CAUs) to establish baseline information on crustose coralline red algae and scleractinian corals in the NWHI. Data collected by the CAUs will enable monitoring of changes in growth rates and other properties of these critical reef-building organisms as oceans become more acidic under expected climate change.

Coincident with the cruise, NOAA's Coral Reef Watch issued an alert of widespread bleaching in parts of the Pacific expected to occur from September through December 2010. To better understand coral reef ecosystem responses, Pacific RAMP scientists began monitoring conditions across the Hawaiian Archipelago. In the north and northwest backreef areas at Kure Atoll, scientists on the Hi'ialakai reported up to 100% bleaching of a single species, Montipora capitata, in localized areas at depths less than 3 m. Chief Scientist Vroom, however, noted that the overall degree of bleaching was similar to levels reported on research cruises in 2008 and 2009 when no alert was issued. He also noted that no dead corals were observed associated with this 2010 bleaching event.

At French Frigate Shoals, divers observed several overturned table corals, possibly an effect of Hurricane Neki, which passed directly over French Frigate Shoals in October 2009. Fish populations were surveyed at 118 Rapid Ecological Assessment (REA) sites selected using a random stratified design, and surveys of benthic communities and habitats were conducted at 46 REA sites. Also, 76 towed-diver surveys were completed, covering 165 km of reef.

A Spanish dancer nudibranch swims in waters near Maui.  NOAA photos by Jill Samzow. A Spanish dancer nudibranch swims in waters near Maui.  NOAA photos by Jill Samzow.
A Spanish dancer nudibranch swims in waters near Maui. NOAA photos by Jill Samzow.

After a brief return to Ford Island, Pearl Harbor, to replenish provisions and refresh the scientific field party, the Hi'ialakai embarked in early October on a second Pacific RAMP cruise to survey coral reefs in the main Hawaiian Islands. CRED scientists were joined by partners from the University of Hawai'i Joint Institute for Marine and Atmospheric Research and San Diego State University for a 27-day expedition. Chief Scientist for this cruise was CRED researcher Bernardo Vargas-Ángel. The team surveyed fish populations at 159 Rapid Ecological Assessment (REA) sites selected using a random stratified design, and surveyed benthic communities and habitats at 78 REA sites. It also completed 127 towed-diver surveys, covering 294 km of reef. At an additional 25 REA sites around O'ahu, fish surveys were conducted via shore-based operations.