Exploring the Climate Change Refugia Potential of Equatorial Pacific Coral Reefs

Elizabeth Joan Drenkard, Ph.D., 2015
Anne Cohen, Co-advisor
Daniel McCorkle, Co-advisor
Kristopher Karnauskas, Co-advisor

Global climate models project a 21st century strengthening of the Pacific Equatorial Undercurrent (EUC). The consequent increase in topographic upwelling of cool waters onto equatorial coral reef islands would mitigate warming locally and modulate the intensity of coral bleaching. However, EUC water is potentially more acidic and richer in dissolved inorganic nutrients (DIN), both widely considered detrimental to coral reef health.

My analysis of the Simple Ocean Data Assimilation product indicates that the EUC has indeed strengthened over the past 130 years. This result provides an historical baseline and dynamical reference for future intensification. Additionally, I reared corals in laboratory experiments, co-manipulating food, light and CO₂ (acidity) to test the role of nutrition in coral response to elevate CO₂ conditions: Heterotrophy yields larger corals but CO₂ sensitivity is independent of feeding. Conversely, factors that enhance zooxanthellate photosynthesis (light and DIN) reduce CO₂ sensitivity. Corals under higher light also store more lipid but these reserves are not utilized to maintain calcification under elevated CO₂. My results suggest that while mitigation of CO₂ effects on calcification is not linked to energetic reserve, EUC fueled increases in DIN and productivity could reduce effects of elevated CO₂ on coral calcification.