Abstract

The Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve (Reserve) was created in 2000 to facilitate the long-term conservation and protection of the coral reef ecosystem and related marine resources of the Northwestern Hawaiian Islands (NWHI). Nearly 70 percent of the coral reefs in the United States are in the NWHI, and this pristine coral reef ecosystem presents unique challenges for management and opportunities for research. The Reserve's coral reef research program in the NWHI focuses on basic habitat characterization and monitoring, as well a documentation of marine resources of the NWHI.

In September 2002, a multi-disciplinary collaborative expedition was sponsored by the Reserve to document the biological, cultural, and historical resources of the NWHI. These reef surveys recorded the diversity and abundance of fishes, algae, corals, and other reef invertebrates at numerous locations throughout the archipelago. Historical and cultural resources such as shipwrecks were also documented on shallow reefs by maritime archaeologists. The results of these coral reef research efforts will aid in the creation of management plans for the largest coral reef system in the United States.

The most significant outcome of the expedition was documentation of the first major coral bleaching event to be recorded in the NWHI. Bleaching was most pronounced in shallow backreef and reef flat habitats exposed to the most intense sunlight and ultraviolet radiation. Mortality due to bleaching was also highest in these habitats. Susceptibility to bleaching differed between species. Rice corals (Montipora species) and cauliflower corals (Pocillopora species) were most susceptible to bleaching, whereas lobe corals and finger corals (Porites species) were rarely bleached. Midway Atoll had the highest frequency of bleaching, with noticeably bleached coral colonies noted at 73 percent of the sites surveyed. A follow-up survey of Midway Atoll in December 2002 found that many of the previously bleached corals were recovering and that mortality was not a high as was originally anticipated. Ongoing studies will continue to document the recovery of these coral reefs.