Project: Physiological Mechanisms for CO2-sensing and Related Intracellular Signaling Pathways in Corals

Carbon dioxide has been rapidly accumulating in the atmosphere over the past 200 years as a by-product of the modern industrialized human lifestyle. A large portion of this excess carbon dioxide is dissolving in the oceans, producing hydrogen ions that lower the pH of the water, thus making it more acidic. Because the current rate of ocean acidification is faster than the most rapid rates recorded in the geological record, it is unclear whether marine organisms will be able to survive and adapt to these rapid changes in ocean chemistry. Coral reefs are among the most vulnerable organisms to ocean acidification owing to their calcium carbonate skeleton that dissolves at more acidic pH. Moreover, the deleterious effects of ocean acidification on corals may also extend to fertilization, metabolism and to the essential relationship between corals and their symbiotic algae. However, the lack of information on basic coral cell physiology precludes predicting the effects of ocean acidification based on strict chemical and mechanistic models. The limits to our knowledge about the basic biology of corals in turn limits the effectiveness of policy-making and managerial decisions about these important marine resources.

This project will characterize the molecular and cellular mechanisms used by corals to sense carbon dioxide, pH and bicarbonate, their associated signal transduction pathways, their roles in regulating physiology, and their responses to ocean acidification. This project will use a suite of experimental techniques, including in vitro biochemical assays with recombinant proteins; real-time microscopy imaging of coral cell cultures to determine regulation of intracellular pH, calcification and biofluorescence; and respirometry experiments with live coral fragments. Therefore, this study will characterize coral physiological responses to ocean acidification over the broad spectrum from molecules, to cells to whole organisms.

This research has the potential to generate mechanistic models to explain and predict the effects of ocean acidification on corals, thereby complementing ongoing and future physiological, transcriptomic and genomic studies, while also bridging fundamental research on coral physiology with coral reef management. Other broader impacts of this research include mentoring of young scientists at various stages of their careers (several volunteers, undergraduate and graduate students and one postdoctoral researcher). The project establishes interdisciplinary research collaborations with intramural, national and international laboratories, particularly with researchers at Centre Scientifique de Monaco. A museum exhibit will be developed at the Birch Aquarium at Scripps to enhance public awareness of ocean acidification. Together with a series of public lectures and online resources, these activities will reach approximately 400,000 children and adults that attend the Birch Aquarium annually, and millions of online viewers.