Coral reefs are among the most diverse ecosystems on the planet, housing an estimated 25% of marine species.  Global climate models predict that by the end of this century, tropical seawater temperatures will be up to 3ÁC warmer than they are today and at least twice as acidic, which threatens the long-term survival of coral reef ecosystems.  Elevated temperature and ocean acidification have been shown to cause reduced coral growth rates and increased coral disease and mortality rates.  To date, the assumption has been that corals will not be able to adapt because the rates of anthropogenically driven ocean acidification and climate change are too high.  This study aims to measure changes in coral physiology to determine if coral adapt or acclimatize to global change.  If they can adapt, how fast is the adaptation rate?  How do adaptation rates differ among species and geographic locations? Answers to these questions are key to developing strategic coral conservation and management plans.  To address these questions, eight species of Hawaiian corals will be studied using a two-part approach:  1) a survey of natural corals found across natural temperature and acidity gradients and 2) a two-year mesocosm study which will expose corals collected in part 1 to temperature and acidity conditions expected at the end of this century. This work is especially important in Hawaii for preserving coral biodiversity in a UNESCO World Heritage Site - the Papahanaumokuakea Marine National Monument (PMNM).  PMNM encompasses the northwestern Hawaiian Islands, is renowned as one of the most pristine and highly protected coral reefs remaining on the planet, and is one of the largest marine conservation areas in the world. This research will also provide critical data input for models used to project the persistence of reefs in the future.  Findings from this work will be communicated at scientific meetings, through peer-reviewed journal publications, and via press releases, public lectures, website platforms, and classroom teaching.  This project will train future scientists (one PhD student, 3 undergraduates, and 2 high school students) and provide an environment that will foster their passion and skills necessary to pursue career options in science.  Thus, this work has the potential to transform our conceptual and empirical understanding of how corals respond to rapid environmental change and make an impact on coral conservation efforts and education.This study will test the assumption that corals will not be able to adapt because the rates of anthropogenically driven ocean acidification and climate change are too high.  The investigators will quantitatively measure changes in coral physiology to determine if coral adapt or acclimatize to global change.  In brief, this study proposes to evaluate the adaptation and acclimatization capacity of eight species of Hawaiian corals to long-term exposure of elevated temperature and ocean acidification (OA) conditions using a two-part approach:  1) a survey of natural corals found across natural temperature and pCO2 gradients and 2) a two-year mesocosm study where corals collected in part 1 to a range of temperature and pCO2 conditions expected this century.  In both approaches, the phenotypic (i.e., physiological and biogeochemical) responses of corals to future climate change will be measured by the investigator in conjunction with the genotypic (i.e., genomic and transcriptomic) responses of the same corals.  This study will address variation at both the population and species level.  It will also be the first study to examine the effects of elevated temperature and pCO2 on corals in replicated mesocosms over a multiannual timeframe with a comprehensive suite of physiological, biogeochemical, and genomic tools.  The proposed study includes ~97% of the coral species in the Hawaiian archipelago, yielding extensive spatial and biological relevance for the study.