Kenyon, J. C., Brainard, R. E.

Second recorded episode of mass coral bleaching in the Northwestern Hawaiian Islands

2006

Atoll Research Bulletin

543

505-523

"Mass coral bleaching involves multiple species over large areas. A second known episode of mass bleaching was documented in the Northwestern Hawaiian Islands (NWHI) during September/October 2004. Bleaching was observed in 10 species of the three dominant genera (Porites, Pocillopora, Montipora). Spatial and taxonomic patterns of bleaching in 2004 bore many similarities to a 2002 bleaching event, the first ever recorded from this region. The incidence of bleaching was higher at the three northern atolls (Pearl and Hermes, Midway, Kure) than at Lisianski and reefs farther south in the NWHI. At these northern atolls, the incidence of bleaching was higher in shallow backreef and patch reef habitats than on the deeper forereef. In both years, the combined influence of depth and the relative abundance/differential susceptibility of coral taxa underlay the salient spatial patterns of bleaching. In both years, the backreef habitat at Pearl and Hermes Atoll experienced the highest levels of bleaching. Montipora, among the genera most susceptible to bleaching, experienced extensive mortality and algal overgrowth in backreef habitats at the three northern atolls following the 2002 event. In situ subsurface temperature recorders, which registered water temperatures at 22 shallow backreef and lagoon sites, indicate corals experienced temperatures exceeding local bleaching thresholds for substantially longer periods of time in 2004 than in 2003, when only low levels of bleaching were observed. The occurrence of two episodes of mass bleaching over a period of three calendar years lends credence to predictions that the frequency of bleaching events will increase."

FY2004 CRCP Project ID 1221; Project Title: Long-Term Monitoring of Benthos (Coral, Other Invertebrates, Algea): Rapid Ecological Assessments at all U.S. Pacific Islands; Principal Investigator: Rusty Brainard. ASFA