New manuscript shows that internal wave cooling may provide global-scale refuge from coral bleaching

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Lauren Toth (Research Oceanographer, SPCMSC) published a manuscript this week with academic collaborators showing that the cooling provided to many coral-reef environments by internal waves mitigated thermal stress during the 2015–2016 global El Niño event.

Photo shows white, bleached coral surrounded by brown coral, with fish swimming

Photograph of shallow-water coral bleaching at Sombrero de Pelo reef in Pacific Panama during the 2015-2016 El Niño event. Because of the influence of internal waves, corals growing at deeper locations at this site did not bleach. (Credit: Lauren Toth, USGS. Public domain.)

A study published this week in Nature Geoscience by SPCMSC Research Oceanographer Lauren Toth and academic colleagues describes how high-frequency internal waves modulated warming on coral reefs across the Pacific Ocean during the 2015–2016 global El Niño event. Elevated water temperatures, such as those that occurred throughout the tropics during the 2015–2016 El Niño event, threaten shallow-water coral reefs because they cause coral bleaching and bleaching-related coral mortality. Recently studies have suggested, however, that a large proportion of reef habitats occur at intermediate depths (>10–20 m), where temperatures may be more variable as a result of mixing with deeper, cooler waters through internal waves. The researchers evaluated the impact of internal waves on heat accumulation during the 2015–2016 El Niño using in situ temperature records across a depth range of 50 m at three sites spanning the Pacific Ocean: Panama, French Polynesia, and Japan. They showed that internal waves significantly reduced heat accumulation and decreased the potential for coral bleaching by more than 30%, suggesting that internal waves may provide a widespread refuge for coral reefs from thermal stress in the future.

The publication can be found at

This research was conducted as part a NSF-funded project awarded to Toth and collaborators at Florida Institute of Technology, and Scripps Institution of Oceanography and the CMHRP CREST project. It was conducted in collaboration with researchers at the Hong Kong University of Science and Technology, Scripps Institution of Oceanography, Florida Institute of Technology, and University of Tokyo.

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Date published: October 5, 2018
Status: Active

Coral Reef Ecosystem Studies (CREST)

The specific objectives of this project are to identify and describe the processes that are important in determining rates of coral-reef construction. How quickly the skeletons of calcifying organisms accumulate to form massive barrier-reef structure is determined by processes of both construction (how fast organisms grow and reproduce) and destruction (how fast reefs break down by mechanical...