Preliminary Results of Patterns of 2019 Thermal Stress and Coral Bleaching Across the Hawaiian Archipelago

Winston, Morgan; Couch, Courtney S.; Huntington, Brittany; Vargas-Ángel, Bernardo; Suka, Rhonda; Oliver, Thomas; Halperin, Ariel; Gray, Andrew K.; McCoy, Kaylyn; Asbury, Mollie; Barkley, Hannah C.; Gove, Jamison M.; Smith, Darren; Kramer, Lindsey; Rose, Julia; Conklin, Eric; Sukhraj, Nadeira; Morioka, James

doi:10.25923/8pqg-tq06

Cited by 3 publications

(2 citation statements)

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“…The results of this study show that corals in Kaneʻohe Bay experienced a moderate to severe bleaching event in 2019, with up to 80% of corals showing some signs of stress during this period. In general, reefs around O'ahu did bleach more extensively (~43%) than other Hawaiian islands during the 2019 event (Winston et al, 2020). Variation in bleahing severity in Kaneʻohe Bay was mediated by sediment levels and species composition, while mortality was driven largely by temperature and the identity of the coral.…”

Section: Discussionmentioning

confidence: 95%

Fine-scale variability in coral bleaching and mortality during a marine heatwave

et al. 2023

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Coral bleaching and mortality can show significant spatial and taxonomic heterogeneity at local scales, highlighting the need to understand the fine-scale drivers and impacts of thermal stress. In this study, we used structure-from-motion photogrammetry to track coral bleaching, mortality, and changes in community composition during the 2019 marine heatwave in Kāneʻohe Bay, Hawaiʻi. We surveyed 30 shallow reef patches every 3 weeks for the duration of the bleaching event (August-December) and one year after, resulting in a total of 210 large-area, high-resolution photomosaics that enabled us to follow the fate of thousands of coral colonies through time. We also measured environmental variables such as temperature, sedimentation, depth, and wave velocity at each of these sites, and extracted estimates of habitat complexity (rugosity R and fractal dimension D) from digital elevation models to better understand their effects on patterns of bleaching and mortality. We found that up to 80% of corals experienced moderate to severe bleaching in this period, with peak bleaching occurring in October when heat stress (Degree Heating Weeks) reached its maximum. Mortality continued to accumulate as bleaching levels dropped, driving large declines in more heat-susceptible species (77% loss of Pocillopora cover) and moderate declines in heat-tolerant species (19% and 23% for Porites compressa and Montipora capitata, respectively). Declines in live coral were accompanied by a rapid increase in algal cover across the survey sites. Spatial differences in bleaching were significantly linked to habitat complexity and coral species composition, with reefs that were dominated by Pocillopora experiencing the most severe bleaching. Mortality was also influenced by species composition, fractal dimension, and site-level differences in thermal stress. Our results show that spatial heterogeneity in the impacts of bleaching are driven by a mix of environmental variation, habitat complexity, and differences in assemblage composition.

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Section: Discussionmentioning

confidence: 95%

Fine-scale variability in coral bleaching and mortality during a marine heatwave

et al. 2023

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show abstract

“…The results of this study show that corals in Kāne‘ohe Bay experienced a moderate to severe bleaching event in 2019, with up to 80% of corals showing some signs of stress during this period. In general, reefs around O’ahu did bleach more extensively (∼43%) than other Hawaiian islands during the 2019 event (Winston et al 2020). Variation in bleahing severity in Kāne‘ohe Bay was mediated by sediment levels and species composition, while mortality was driven largely by temperature and the identity of the coral.…”

Section: Discussionmentioning

confidence: 99%

Fine-scale variability in coral bleaching and mortality during a marine heatwave

Yadav

Roach

McWilliam

et al. 2022

Preprint

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Coral bleaching and mortality can show significant spatial and taxonomic heterogeneity at local scales, highlighting the need to understand the fine-scale drivers and impacts of thermal stress. In this study, we used structure-from-motion photogrammetry to track coral bleaching, mortality, and changes in community composition during the 2019 marine heatwave in Kāneʻohe Bay, Hawaiʻi. We surveyed 30 shallow reef patches every 3 weeks for the duration of the bleaching event (August-December) and one year after, resulting in a total of 210 large-area, high-resolution photomosaics that enabled us to follow the fate of thousands of coral colonies through time. We also measured environmental variables such as temperature, sedimentation, depth, and wave velocity at each of these sites, and extracted estimates of habitat complexity (rugosity R and fractal dimension D) from digital elevation models to better understand their effects on patterns of bleaching and mortality. We found that up to 80% of corals experienced moderate to severe bleaching in this period, with peak bleaching occurring in October when heat stress (DHW) reached its maximum. Mortality continued to accumulate as bleaching levels dropped, driving large declines in more heat-susceptible species (77% loss of Pocillopora cover) and moderate declines in heat-tolerant species (19% and 23% for Porites compressa and Montipora capitata, respectively). Declines in live coral were accompanied by a rapid increase in algal cover across the survey sites. Spatial differences in bleaching were significantly linked to habitat complexity and coral species composition, with reefs that were dominated by Pocillopora experiencing the most severe bleaching. Mortality was also influenced by species composition, fractal dimension, and site-level differences in thermal stress. Our results show that spatial heterogeneity in the impacts of bleaching are driven by a mix of environmental variation, habitat complexity, and differences in assemblage composition.

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Autumn coral bleaching in Hawai‘i

Jones

Brush

Dilley

et al. 2021

Mar. Ecol. Prog. Ser.

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Coral bleaching in Hawai‘i was first reported in 1996 and subsequently occurred in 2014 and 2015. These largely summer events did not persist past November. In autumn 2019, Hawai‘i experienced persistent warm water until December, resulting in bleaching of many pocilloporid coral colonies, particularly Pocillopora meandrina. We followed the fates of 357 adult P. meandrina and 377 juvenile Pocillopora spp. off Waikīkī on the south shore of O‘ahu. Water temperatures at 5-18 m depth at this site consistently remained above a bleaching threshold of 28°C from September until mid-December. For adult colonies, 96% bleached at least partially, 4% bleached fully, and 11% died by March. Among juvenile colonies, 21% bleached, of which 47% died by March 2020. While mortality was low compared to previous bleaching events in Hawai‘i, such protracted bleaching late into the autumn increases the annual period of temperature stress, which may not bode well for the future of Hawaiian and other high-latitude coral reefs.

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Preliminary Results of Patterns of 2019 Thermal Stress and Coral Bleaching Across the Hawaiian Archipelago

Cited by 3 publications

References 0 publications

Fine-scale variability in coral bleaching and mortality during a marine heatwave

Fine-scale variability in coral bleaching and mortality during a marine heatwave

Fine-scale variability in coral bleaching and mortality during a marine heatwave

Autumn coral bleaching in Hawai‘i

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