Kenyon, J. C., Wilkinson C. B., Aeby G. S.

Community structure of hermatypic corals at Midway Atoll in the Northwestern Hawaiian Islands: a legacy of human disturbance

2010

Atoll Research Bulletin

581

1-26

"Percent cover of shallow-water (less than 20 m depth) scleractinian corals at Midway Atoll, a classic atoll in the Northwestern Hawaiian Islands (NWHI), was quantified from analysis of imagery recorded along more than 49 km of benthic habitat by towed divers and at 26 sites surveyed with video transects and photoquadrats during 2002 and 2003. Colony densities and size class distributions were determined from censuses within belt transects at the same sites. All three methods showed statistically significant differences in total coral cover and relative abundance of coral genera among three habitats (fore reef, back reef, and lagoon). Mean coral cover was sparse (less than 1.6 percent) on both the fore reef, which was dominated by massive and encrusting growth forms of Porites, and in the lagoon (less than 1.2 percent), which was dominated by Pocillopora. Mean coral cover was highest on the back reef (greater than 13.5 percent), which was dominated by Montipora. All taxa showed habitat-specific differences in colony density while the two most widespread genera, Porites and Pocillopora, showed differences in habitat-specific size class distributions. Midway has the lowest system-wide and habitat-specific mean coral cover of the seven reef systems in the NWHI that have been surveyed with similar methods during a comparable time period, which is likely related to its history of human use and modification. Bleaching history, disease prevalence, crown-of-thorns seastars, marine debris, larval recruitment, and alien benthic invertebrates are discussed as other influential factors shaping the observed coral community. As the most comprehensive description of Midway coral communities produced to date, these data provide a valuable baseline for assessing future change."

FY2009 CRCP Project ID 1221; Project Title: Pacific Reef Assessment and Monitoring Program (Pacific RAMP): Biennial Monitoring for the U.S. Pacific Islands and Atolls; Principal Investigator: Rusty Brainard