Abstract
Due to anthropogenic activities, there has been a dramatic increase in atmospheric carbon dioxide, which interacts with seawater, making it more acidic. Ocean acidification is negatively impacting coral reefs, which are already under stress from rising temperatures. In order to mitigate the effects of climate change, negative emission technologies, such as ocean alkalinity enhancement (OAE), should be tested. Increasing the alkalinity of the ocean will impact calcifying organisms in yet undetermined ways. The purpose of this study was to determine how corals respond to increased alkalinity during thermal stress. To test this, corals were placed in four tanks, two control and two alkaline, and the water temperature was increased to 32oC. Various aspects of coral health such as calcification, tissue properties, and survivorship were analyzed throughout the course of experiment. Alkalinity was increased through the addition of magnesium hydroxide, and total alkalinity and pH of the seawater were measured to ensure a difference in water chemistries between the control and treatment tanks. There was a significant difference in pH (p=3.039e-07), pCO2 (p=0.000542) and aragonite saturation (p=4.874e-07) between the control and treatment tanks, and increased alkalinity had no significant impact on any aspect of coral physiology during heat stress (p>0.05). These results suggest that if OAE is used as a form of climate mitigation, corals may not be negatively impacted by the addition of alkalinity, even during heat stress events