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Full text release has been delayed at the author's request until May 10, 2026

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Physiological Adaptations in Hawaiian Corals to Global Climate Change

McLachlan, Rowan H
http://orcid.org/0000-0002-7222-8210
http://rave.ohiolink.edu/etdc/view?acc_num=osu1618130622086699

Abstract Details

2021, Doctor of Philosophy, Ohio State University, Earth Sciences.
The distribution and abundance of coral reef ecosystems is declining globally due to the detrimental impacts of climate change. As the surface ocean becomes warmer and more acidic, corals must adapt or acclimatize in order to survive and persist. The overarching goal of my dissertation was to evaluate the biological processes that lead corals to adapt and acclimatize to the levels of ocean warming and acidification expected later this century. Following a review of 255 coral heat-stress experiments conducted over the last thirty years (Chapter 2), I identified several gaps in our knowledge of coral bleaching. For instance, the majority of experimental coral bleaching research has been conducted on only three Scleractinian coral species, many reef regions worldwide are critically understudied, and the literature is heavily biased towards adult life stages (as opposed to gametes, larvae, recruits). Similarly, the majority of studies are short-term in duration (i.e., < 7 days) and focus on only one or two aspects of coral biology (e.g., calcification or photosynthetic efficiency). Thus, our understanding of the long-term impacts of global climate change on coral holobiont physiology is lacking. To better understand the link between holobiont physiology and the environment, I conducted a comprehensive survey of Oʻahu coral reefs (Chapter 3), including eight species collected from six reef locations. I found that environmental gradients of temperature, significant wave height, and seawater chlorophyll concentration were strongly correlated with the physiological profiles of Hawaiian corals, though the strength of this relationship was species specific. My results indicate that Montipora capitata and Pocillopora acuta have the most physiological variance along environmental gradients, suggesting a higher capacity for adaptation or acclimatization. Conversely, Porites evermanni and Pocillopora meandrina have the least physiological variance which does not correlate strongly with habitat conditions. To further investigate the adaptive capacity of Hawaiian corals to sustained future ocean warming and acidification, I conducted a long-term mesocosm experiment (Chapter 4) and documented mortality rates and assessed changes in holobiont physiological profiles in Montipora capitata, Porites compressa and Porites lobata. All species suffered substantial mortality following 22-months exposure to elevated temperature and pCO2, however many individuals were able to survive. Coral skeletal and tissue growth and energy reserves were maintained in the surviving populations of each species. However, M. capitata suffered significant paling due to bleaching, and some individuals were unable to meet metabolic demand. These results indicate that if exposure to future ocean conditions is greater than 22-months, M. capitata may suffer increased mortality and loss of genetic diversity. Given the heterotrophic nature of this species, in the wild where demersal zooplankton concentrations are higher than those present in our experiment, M. capitata will likely fare better. Overall, this long-term, ecologically relevant, and holobiont-integrative experiment revealed that there is hope that at least half of Hawaiian corals will survive and persist in the future if carbon dioxide concentrations are controlled within the boundaries pledged as part of the Paris Climate Agreement.
Andréa Grottoli (Advisor)
Agustí Muñoz-Garcia (Committee Member)
Lawrence Krissek (Committee Member)
Robert Toonen (Committee Member)
Noah Weisleder (Committee Member)
251 p.
Biogeochemistry; Biology; Climate Change; Earth; Ecology; Environmental Science; Oceanography
coral; physiology; ocean warming; ocean acidification; adaptation; acclimatization; Montipora; Porites; Pocillopora

Recommended Citations

Citations

  • McLachlan, R. H. (2021). Physiological Adaptations in Hawaiian Corals to Global Climate Change [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618130622086699

    APA Style (7th edition)

  • McLachlan, Rowan. Physiological Adaptations in Hawaiian Corals to Global Climate Change. 2021. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1618130622086699.

    MLA Style (8th edition)

  • McLachlan, Rowan. "Physiological Adaptations in Hawaiian Corals to Global Climate Change." Doctoral dissertation, Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618130622086699

    Chicago Manual of Style (17th edition)

osu1618130622086699
© 2021, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.