Responses of Stress-Tolerant Corals to Ocean Acidification

Increased atmospheric pCO2 is expected to reduce coral calcification through increased temperatures (global warming) and decreased pH (ocean acidification). Two species of corals found in Florida Bay, Solenastrea hyades and Siderastrea radians, exhibit high stress tolerance, persisting in an environment where seasonal swings in temperature and salinity often exceed tolerance limits for most other species of coral. The persistence of these two species in this marginal environment may provide insights into mechanisms of resilience to climate change stress. In other words, does tolerance to broad swings in physical environmental parameters also convey a tolerance to swings in the carbonate chemistry of Florida Bay water, which is also much broader than encountered in most coral reef environments? This dissertation combines laboratory and field studies to characterize the growth responses of stress tolerant corals to increased pCO2 across a range of temperatures. Several Caribbean species were incorporated into the laboratory studies to provide comparisons across species. The role of the environment in determining coral responses to ocean acidification was investigated, as well as the utility of determining historical conditions from coral skeletal proxies. This dissertation demonstrates 1) the potential of a coral in Florida Bay to preserve signals of water quality conditions including anomalous events in its skeleton, 2) stress-tolerant corals are still vulnerable to ocean acidification, 3) corals may face a trade-offs between calcification and stress tolerance, and 4) species-specific responses to simulated climate change (increased temperature and pCO2)