Algal monitoring studies on remote Tropical Pacific reefs

Coral reefs of US-held islands in the central Pacific Ocean are among the most pristine in the world and represent over 93% of the reef systems under United States jurisdiction. The remote location of many islands has limited past algal research, resulting in incomplete understanding of species diversity, quantity, and ecology. Starting in 2000, the Coral Reef Ecosystem Investigation (CREI) began rapid ecological assessments on many Pacific island reefs to monitor ecological changes in reef biota over time. During the past year, algal efforts have concentrated on the French Frigate Shoals (Northwestern Hawaiian Islands) where we have increased the number of algal species reported by 1000%. Additionally, species new to science, including Acrosymphyton brainardii and Scinaia huismanii, have been described. Quantitative field sampling using a photoquadrat method is revealing species of the green algae Halimeda and Microdicyton to be ecological dominants in many areas during late summer/early autumn. Preliminary analyses with Primer software show species composition and abundance of all benthic organisms to differ significantly between most field sites sampled. Additional benthic habitat mapping of Pacific island reefs by CREI researchers is breaking the long-held paradigm that macroalgal cover is minimal in healthy tropical reef systems. Videotape analyses of benthic communities often find over 50% algal cover from 1 to 20 meter depths in many locations. Common ratios of macroalgae, turf algae, and crustose coralline algae to corals, other benthic organisms and substrate types on US Pacific reefs are being calculated for the first time.