Coral reef resilience to thermal stress in the Eastern Tropical Pacific

• Published in: Global change biology 2020-07, Vol.26 (7), p.3880-3890
• Main Authors: Romero‐Torres, Mauricio, Acosta, Alberto, Palacio‐Castro, Ana M., Treml, Eric A., Zapata, Fernando A., Paz‐García, David A., Porter, James W.
• Format: Article
• Language: English
• Subjects: Anomalies; Climate change; Coral bleaching; coral cover; Coral reefs; Corals; degree heating weeks; Dolphins & porpoises; Eastern Tropical Pacific; ecosystem resilience; El Nino; El Nino phenomena; ENSO; Heat stress; Heat tolerance; Recovery; Resilience; Southern Oscillation; Survival; Thermal stress; Tropical climate
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.15126

Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño‐Southern Oscillation (ENSO) events originating in the Eastern Tropical Pacific (ETP). El Niño‐induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan‐tropical collapse of coral reefs. During the 1982–1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997–1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970–2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970–2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño‐stressed conditions, often recovering from these events in 10–15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near‐term future climate‐change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios. El Niño is the main threat to coral reefs in the Eastern Tropical Pacific (ETP), but it is unknown if the coral cover decreases in the long term due to El Niño‐induced thermal stress. Based on a 44 year time‐series analysis of live coral cover (1970–2014), we determine that, unlike in the Caribbean and the Indo‐Pacific, coral reefs in the ETP do not show a long‐term decline. Our analysis indicates that ETP coral reefs show recovery patterns of 10–15 years, allowing them to persist under El Niño‐stressed conditions. We explore some possible explanations for this resilience to thermal stress.