Project: Ocean Acidification: Coral reef adaptation and acclimatization to global change: resilience to hotter, more acidic oceans

NSF Award Abstract:

Coral reefs house one-quarter of all marine species and provide over a billion people around the world with food, jobs, and protection from storms. In spite of their high biodiversity and value, coral reefs appear to be particularly vulnerable to ocean acidification, a consequence of increased atmospheric carbon dioxide. Many calcifying reef organisms have reduced growth rates and their reproduction is disrupted under these conditions. Likewise the accompanying higher average sea temperatures can lead to coral bleaching, directly killing corals or increasing disease outbreaks. Combined, these impacts may be too much for many coral species to cope with, leading to predictions of degradation and collapse of these incredible ecosystems over the next few decades. This study examines the eight dominant Hawaiian coral species that constitute >95% of the coral cover across the archipelago, yielding broad relevance for the data. Further, the corals include two species-complexes currently being considered for listing under the U.S. Endangered Species Act. The results will be used to develop adaptive management plans for preserving biodiversity in a World Heritage Site, the Papahanaumokukea Marine National Monument, which is renowned as one of the most pristine and highly protected coral reefs remaining on the planet. This project provides a critical link between short-term, single-species studies and coral reef community responses to global change relevant to other marine ecosystems across the globe. Training opportunities for a post doctoral scholar, graduate students, and undergraduate students are provided, along with opportunities for local K-12 students. Outreach includes broad communication of the findings through interactive K-12 education, interactions with the Waikiki Aquarium, a rush-hour talk radio show, direct engagement with local resource managers, and an international blog.

Different coral species, and even different individuals of the same species, are known to vary in their tolerances to lower pH and higher temperature. Thus, it is important to know if the environment is changing too quickly for corals and coral reefs to respond effectively, or could acclimatization or adaptation of corals play a significant role in the future of reefs? The role of chronically reduced seawater pH and elevated seawater temperature on corals and on the diverse coral reef communities that rely upon, and live within, them are examined. First, the capacity for corals to regulate pH at their site of calcification after acclimation to a range of seawater pH and temperature using confocal microscopy and pH-sensitive vital dyes will be assessed to understand the influence of previous history (acclimatization) and fixed, heritable differences (adaptation) on the capacity of an individual coral to tolerate changes in the environment. Second, the potential for corals to acclimatize to lower pH and higher temperature will be empirically estimated in a two year mesocosm experiment including all eight of the dominant Hawaiian coral species. The range of physical environments will be characterized and the patterns of population connectivity will be investigated for the focal coral species across sampling locations to assess the potential for local adaptation. Finally, because relatively little is known about the impacts of low pH and higher ocean temperature on reef organisms other than corals, yet these thousands of other species comprise the bulk of reef biodiversity and perform important ecological functions on coral reefs, a two-year mesocosm study will examine the effects of chronically reduced pH and elevated temperature on the biodiversity, community structure, and ecosystem function of biologically diverse coral reef communities.