Upwelling systems: potential climate change refugia for reef-building corals in the Eastern Tropical Pacific

This proposal integrates across the biosphere and hydrosphere, seeking to understand how corals can survive marine heatwaves. We will use natural laboratories in the north Pacific coast of Costa Rica to explore the environmental conditions that may influence the response of reef-building corals to climate change. Specifically, in situ benthic imagery and variable fluorescence measurements (both non-invasive methods) will be used to obtain high-resolution long-term data on the bleaching/mortality and physiological response of corals to the individual and combined effects of ocean warming and acidification during El Nino-related thermal events in upwelling and non-upwelling sites. One site is in Culebra Bay, in the Gulf of Papagayo (Guanacaste) and the other is in Sámara, further south, close to the Gulf of Nicoya (Puntarenas). Strong seasonal upwelling in the Gulf of Papagayo results in cooler, more nutrient rich, and more acidic seawater conditions between December and May each year. Despite these naturally acidified waters, corals here show the highest linear extension rates in the Eastern Pacific, suggesting that the colder and nutrient-rich waters in the Gulf of Papagayo may, therefore, serve as a refugia environment for corals as the frequency and intensity of marine heatwaves increase due to anthropogenic climate change. Seasonal upwelling is much less pronounced and waters are on average warmer and more nutrient-limited further south, close to the Gulf of Nicoya. Map of the two locations along the Eastern Tropical Pacific coast of Costa Rica, namely (b) Gulf of Papagayo, Guanacaste, Costa Rica (10.608739N 85.703523W), and (c) Sámara bay, Puntarenas, Costa Rica (9.864684N 85.51266W).