Coral reef carbonate accretion rates track stable gradients in seawater carbonate chemistry across the U.S. Pacific Islands

Hannah C. Barkley, Thomas A. Oliver, Ariel A. Halperin, Noah V. Pomeroy, Joy N. Smith, Rebecca M. Weible, Charles W. Young, Courtney S. Couch, Russell Eugene Brainard, Jennifer C. Samson

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The U.S. Pacific Islands span a dramatic natural gradient in climate and oceanographic conditions, and benthic community states vary significantly across the region’s coral reefs. Here we leverage a decade of integrated ecosystem monitoring data from American Samoa, the Mariana Archipelago, the main and Northwestern Hawaiian Islands, and the U.S. Pacific Remote Island Areas to evaluate coral reef community structure and reef processes across a strong natural gradient in pH and aragonite saturation state (Ωar). We assess spatial patterns and temporal trends in carbonate chemistry measured in situ at 37 islands and atolls between 2010 and 2019, and evaluate the relationship between long-term mean Ωar and benthic community cover and composition (benthic cover, coral genera, coral morphology) and reef process (net calcium carbonate accretion rates). We find that net carbonate accretion rates demonstrate significant sensitivity to declining Ωar, while most benthic ecological metrics show fewer direct responses to lower-Ωar conditions. These results indicate that metrics of coral reef net carbonate accretion provide a critical tool for monitoring the long-term impacts of ocean acidification that may not be visible by assessing benthic cover and composition alone. The perspectives gained from our long-term, in situ, and co-located coral reef environmental and ecological data sets provide unique insights into effective monitoring practices to identify potential for reef resilience to future ocean acidification and inform effective ecosystem-based management strategies under 21st century global change.
Original languageEnglish (US)
JournalFrontiers in Marine Science
StatePublished - Nov 24 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-12-14
Acknowledgements: This work was funded by the NOAA Ocean Acidification Program and the NOAA Coral Reef Conservation Program (project #743), as part of the NOAA National Coral Reef Monitoring Program. We thank the officers and crew of the NOAA Ships Hiʻialakai, Oscar Elton Sette, and Rainier for providing operational support for Pacific RAMP/NCRMP missions, as well as the numerous NOAA scientific staff and partners who have collected field data over a decade of long-term coral reef monitoring surveys. We thank Kevin Trick, Annette DesRochers, Michael Akridge, and Brooke Olenski for extensive assistance with the management, quality control, and archival of data; Dana Greeley, Morgan Ostendorf, Julian Herndon, and Simone Alin for conducting laboratory analysis of carbonate chemistry samples; and Brittany Huntington and Bernardo Vargas-Ángel for advice on benthic data analysis and interpretation. Pacific RAMP/NCRMP ocean acidification sampling design, survey methodologies, and early data collection were designed, developed, and implemented with input from Richard Feely, Christopher Sabine, Elizabeth Jewett, Adrienne Sutton, Simone Alin, and in close collaboration with the NOAA Ocean Acidification Program and NOAA Coral Reef Conservation Program. We also acknowledge the many partner agencies — including the Papahānaumokuākea Marine National Monument, Pacific Remote Islands Marine National Monument, Rose Atoll Marine National Monument, Marianas Trench Marine National Monument, US Fish and Wildlife Service, US National Park Service, American Samoa Department of Marine and Wildlife Resources, National Marine Sanctuary of American Samoa, State of Hawaii Department of Land and Natural Resources, Commonwealth of the Northern Mariana Islands (CNMI) Division of Fish and Wildlife, CNMI Division of Coastal Resources Management, and Guam Division of Aquatic and Wildlife Resources — who have supported field operations, provided input on research priorities, and granted research permits to collect the data presented here.


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