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1. Ocean currents magnify upwelling and deliver nutritional subsidies to reef-building corals during El Niño heatwaves

   https://doi.org/10.1126/sciadv.add5032  

   Fox, Michael D.; Guillaume-Castel, Robin; Edwards, Clinton B.; Glanz, J.; Gove, Jamison M.; Green, J. A.; Juhlin, E.; Smith, Jennifer E.; Williams, Gareth J. (June 2023, Science Advances)

   Marine heatwaves are triggering coral bleaching events and devastating coral populations globally, highlighting the need to identify processes promoting coral survival. Here, we show that acceleration of a major ocean current and shallowing of the surface mixed layer enhanced localized upwelling on a central Pacific coral reef during the three strongest El Niño–associated marine heatwaves of the past half century. These conditions mitigated regional declines in primary production and bolstered local supply of nutritional resources to corals during a bleaching event. The reefs subsequently suffered limited post-bleaching coral mortality. Our results reveal how large-scale ocean-climate interactions affect reef ecosystems thousands of kilometers away and provide a valuable framework for identifying reefs that may benefit from such biophysical linkages during future bleaching events. 

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2. Local conditions magnify coral loss after marine heatwaves

   https://doi.org/10.1126/science.abd9464  

   Donovan, Mary K.; Burkepile, Deron E.; Kratochwill, Chelsey; Shlesinger, Tom; Sully, Shannon; Oliver, Thomas A.; Hodgson, Gregor; Freiwald, Jan; van Woesik, Robert (May 2021, Science)

   null (Ed.)

   Climate change threatens coral reefs by causing heat stress events that lead to widespread coral bleaching and mortality. Given the global nature of these mass coral mortality events, recent studies argue that mitigating climate change is the only path to conserve coral reefs. Using a global analysis of 223 sites, we show that local stressors act synergistically with climate change to kill corals. Local factors such as high abundance of macroalgae or urchins magnified coral loss in the year after bleaching. Notably, the combined effects of increasing heat stress and macroalgae intensified coral loss. Our results offer an optimistic premise that effective local management, alongside global efforts to mitigate climate change, can help coral reefs survive the Anthropocene. 

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3. The Costs and Benefits of Environmental Memory for Reef-Building Corals Coping with Recurring Marine Heatwaves

   https://doi.org/10.1093/icb/icac074  

   Brown, Kristen T; Barott, Katie L (June 2022, Integrative and Comparative Biology)

   Abstract Marine heatwaves are occurring more frequently as climate change intensifies, resulting in global mass coral bleaching events several times per decade. Despite the time between marine heatwaves decreasing, there is evidence that reef-building corals can develop increased bleaching resistance across repetitive marine heatwaves. This phenomenon of acclimatization via environmental memory may be an important strategy to ensure coral persistence; however, we still understand very little about the apparent acclimatization or, conversely, sensitization (i.e., stress accumulation or weakening) of reef-building corals to consecutive heatwaves and its implications for the trajectory and resilience of coral reefs. Here, we highlight that not only will some corals become stress hardened via marine heatwaves, but many other individuals will suffer sensitization during repeat heatwaves that further exacerbates their stress response during repeat events and depresses fitness. Under current and predicted climate change, it is necessary to gain a better understanding of the acclimatization vs. sensitization trajectories of different species and individuals on the reef, as well as identify whether changes in bleaching susceptibility relates to physiological acclimatization, trade-offs with other biological processes, and ultimately coral persistence in the Anthropocene. 

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4. Paleo reefs provide clues for contemporary climate-change refugia

   https://doi.org/10.1016/j.crsus.2024.100289  

   van_Woesik, Robert (February 2025, Cell Reports Sustainability)

   Plail, Melissa (Ed.)

   Marine heatwaves are increasing in intensity and frequency, causing worldwide coral bleaching, reductions in coral cover, and shifts in species composition. Recent studies have found, however, that inshore turbid reefs are more resistant to heat stress than offshore clear-water reefs. Inshore turbid reefs, therefore, may play a critical role as climate-change refuges for contemporary coral reefs subjected to marine heatwaves. This perspective explores the importance of inshore reefs in the past, present, and future. Paleo records show that inshore reefs were also crucial as refuges during historically warm periods. Yet, contemporary inshore reefs are especially vulnerable to pollution and land-use-change runoff, which were absent in paleo times. Therefore, inshore reefs need strategic management and protection to maintain their role as climate-change refugia as the oceans continue to warm. 

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5. Repeat bleaching of a central Pacific coral reef overthe past six decades (1960–2016)

   https://doi.org/10.1038/s42003-018-01  

   Hannah C. Barkley1, 6 (October 2018, Communications biology)

   The oceans are warming and coral reefs are bleaching with increased frequency and severity,fueling concerns for their survival through this century. Yet in the central equatorial Pacific,some of the world’s most productive reefs regularly experience extreme heat associated with El Niño. Here we use skeletal signatures preserved in long-lived corals on Jarvis Island to evaluate the coral community response to multiple successive heatwaves since 1960. By tracking skeletal stress band formation through the 2015-16 El Nino, which killed 95% of Jarvis corals, we validate their utility as proxies of bleaching severity and show that 2015-16was not the first catastrophic bleaching event on Jarvis. Since 1960, eight severe (>30%bleaching) and two moderate (<30% bleaching) events occurred, each coinciding with ElNiño. While the frequency and severity of bleaching on Jarvis did not increase over this time period, 2015–16 was unprecedented in magnitude. The trajectory of recovery of this historically resilient ecosystem will provide critical insights into the potential for coral reef resilience in a warming world. 

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