Award: OCE-1657633

Coral reefs provide essential goods and services to millions of people worldwide. Yet the recent rates of ocean warming and local disturbances are jeopardizing the capacity of coral reefs to grow and keep up with the rates of sea-level rise that are associated with climate change. We examined the potential capacity of coral reefs to keep up with rates of sea-level rise along a longitudinal temperature-stress gradient, spanning 142 sites, across the tropical western and central Pacific Ocean. We sought to determine the extent to which habitat differences and environmental variables potentially affected rates of reef growth. In general, we found that the rates of reef growth in the western tropical Pacific Ocean were considerably higher than in the central tropical Pacific Ocean, as the latter region had experienced major temperature stress during the 2014-2017 El Nino. Therefore, temperature anomalies play a significant role in reducing potential reef growth. The low growth rates of coral reefs in the central Pacific, for example at Kiritimati in 2019, equated to approximately ~2 mm y-1 of potential vertical reef growth. Such rates are too low to keep up with projected rates of sea-level rise, except perhaps if greenhouse gases emissions are a significantly reduced (i.e., representative concentration pathway 2.6). We also found that outer barrier and lagoonal reefs had higher rates of reef growth than nearshore reefs. The nearshore reefs do not produce as much carbonate as outer barrier and lagoonal reefs, and therefore do not have as much capacity to grow. Nearshore reefs are also closest to human populations, which make them more vulnerable to sea-level rise than other reef habitats. These results stress the need to protect nearshore reefs from local pollutants and detrimental land-use practices as the oceans continue to warm and as sea level continues to rise. The results of the study suggest that the predicted increase in the intensity and frequency of marine heatwaves will seriously jeopardize reef growth and impede the capacity of coral reefs to keep up with sea-level rise. If reefs lose the capacity to keep up with sea-level rise, island nations that rely on coral reefs as critically important wave barriers are threatened, especially as sea-level rise accelerates and ocean temperatures continue to increase. In terms of the broader impacts, this study developed open-access R code that can be used to calculate carbonate budgets in other localities to (i) predict potential rates of reef growth (i.e., carbonate production rates) and (ii) produce maps to highlight habitats and localities of vulnerability; all the data and R code are deposited at the Woods Hole Biological and Chemical Oceanography Data Management Office (BCO-DMO) (https://www.bco-dmo.org/award/709533). We also ran a data-analysis workshop in Palau, coral-identification workshops in Yap and Pohnpei, a scientific-writing workshop in Majuro, and held seminars at elementary schools and for Senators and other high-level politicians in Kosrae and Kiritimati. In total, we trained over 100 locally influential participants on the importance of coral reefs, their vulnerabilities, and ways to protect them in the Republic of Palau, the Federated States of Micronesia, the Republic of the Marshall Islands, and in the Republic of Kiribati. Last Modified: 05/05/2021 Submitted by: Robert Van Woesik