Marginal Reefs Under Stress: Physiological Limits Render Galápagos Corals Susceptible to Ocean Acidification and Thermal Stress

• Published in: AGU Advances
• Main Authors: Diane Thompson, Malcolm McCulloch, Julia E. Cole, Emma V. Reed, Juan P. D’Olivo, Kelsey Dyez, Marcus Lofverstrom, Janice Lough, Neal Cantin, Alexander W. Tudhope, Anson H. Cheung, Lael Vetter, R. Lawrence Edwards
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: coral reefs; calcification; ocean acidification; heat stress; boron isotopes; biomineralization; Geology; QE1-996.5; Geophysics. Cosmic physics; QC801-809; Ocean acidification
• Online Access: https://doi.org/10.1029/2021AV000509; https://doaj.org/article/df93e2b3afe948a8bc16ab36e3093278

Abstract Ocean acidification (OA) and thermal stress may undermine corals' ability to calcify and support diverse reef communities, particularly in marginal environments. Coral calcification depends on aragonite supersaturation (Ω » 1) of the calcifying fluid (cf) from which the skeleton precipitates. Corals actively upregulate pHcf relative to seawater to buffer against changes in temperature and dissolved inorganic carbon, which together control Ωcf. Here we assess the buffering capacity of modern and fossil corals from the Galápagos Islands that have been exposed to sub‐optimal conditions, extreme thermal stress, and OA. We demonstrate a significant decline in pHcf and Ωcf since the pre‐industrial era, trends which are exacerbated during extreme warm years. These results suggest that there are likely physiological limits to corals' pH buffering capacity, and that these constraints render marginal reefs particularly susceptible to OA.