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Abstract 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.
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This content will become publicly available on June 10, 2026
Impact of El Niño‐Southern Oscillation on the Alkalinity and Salinity of a Coral Reef Lagoon in the Equatorial Pacific—Observations and a Model
Abstract The impacts of El Niño‐Southern Oscillation (ENSO) on salinity and alkalinity in an equatorial coral reef lagoon (Kanton) are investigated using water samples collected in three non‐El Niño years (1973, 2012, and 2018) and one El Niño year (2015). A one‐dimensional, advective‐diffusive model is developed to aid in the interpretation of the sparse observations and make estimates of net ecosystem calcification (NEC) rates. The Kanton lagoon experiences extreme salinity and alkalinity variations driven by ENSO variations in precipitation. During the non‐El Niño years, salinity increases from the ocean (35.5 psu) to the back of the lagoon (38 psu) because evaporation exceeds precipitation, and water resides in the back of the lagoon for ∼180 days. Early in the 2015–2016 El Niño, the back of the lagoon is only ∼1 psu saltier than the ocean because precipitation had begun to exceed evaporation. The model suggests that during El Niño events, when precipitation substantially exceeds evaporation, the back of the lagoon is less salty than the ocean (30–32 psu). Alkalinity variations in the lagoon are primarily due to dilution or concentration driven by the ENSO variations in precipitation and NEC that causes an alkalinity deficit of ∼250 μmol/kg in the back of the lagoon. The estimated NEC rate in 2015 is ∼25% lower (4.1 mmol/day) than in the non‐El Niño years (5.3–5. 7 mmol/day). The NEC rates and coral cover measurements indicate that the Kanton lagoon has recovered from the complete loss of coral cover during the 2002–2003 El Niño.
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- Award ID(s):
- 2049567
- PAR ID:
- 10599557
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 130
- Issue:
- 6
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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