Species intolerant of changing climate might avoid extinction within refugia buffered from extreme conditions. Refugia have been observed in the fossil record but are not well documented or understood on ecological time scales. Using a 37-year record from the eastern Pacific across the two most severe El Nin˜ o events on record (1982–1983 and 1997– 1998) we show how an exceptionally thermally sensitive reef-building hydrocoral, Millepora intricata, twice survived catastrophic bleaching in a deeper-water refuge (.11 m depth). During both events, M. intricata was extirpated across its range in shallow water, but showed recovery within several years, while two other hydrocorals without deep-water populations were driven to regional extinction. Evidence from the subfossil record in the same area showed shallow-water persistence of abundant M. intricata populations from 5000 years ago, through severe El Nin˜ o–Southern Oscillation cycles, suggesting a potential depth refugium on a millennial timescale. Our data confirm the deep refuge hypothesis for corals under thermal stress.
Smith, Tyler B.; Glynn, Peter W.; Maté, Juan L.; Toth, Lauren T.; and Gyory, Joanna, "A Depth Refugium From Catastrophic Coral Bleaching Prevents Regional Extinction" (2014). Ocean Engineering and Marine Sciences Faculty Publications. 74.