Understanding coral bleaching using multi-proxy bleaching reconstruction


The ecosystem services provided by coral reefs are worth over $100 billion annually and include coastline protection, tourism, food and medical derivatives. However, the health of the constituent corals can be significantly impacted by coral bleaching. Coral bleaching (Fig. 1) is the loss of symbiotic zooxanthellae (Symbiodiniaceae) from tropical corals and can be caused by stressors such as thermal perturbations, disease and freshwater runoff. Thermal perturbations are thought to be the most significant bleaching trigger and have been well documented in conjunction with major global bleaching events in 1998, 2002 & 2016. These mass bleaching events caused widespread coral death with catastrophic ecosystem and service provision impacts. The importance of temperature is such that bleaching can now be forecast over a few days – weeks. However, sub-lethal bleaching, where the coral bleaches but recovers, may act as a ‘safety valve’ allowing coral hosts to survive periods of thermal stress in warmer waters. Additionally, other corals and their symbionts are robust to warming-induced bleaching.

Despite the devastation caused by severe coral bleaching, it is still not possible to accurately assess if corals will survive in the warmer oceans projected for the end of the century as we do not understand the interaction between differential drivers of coral bleaching.

Aim: The proposed research aims to reconstruct past coral bleaching using a multi-proxy approach. The record can also be used to assess past frequency and prevalence of coral bleaching and assess whether they are increasing over time. Importantly, it will allow modern observational records of bleaching to be placed into a longer temporal context and to better evaluate the relevance of current bleaching trajectories.


The scholar will have the opportunity to collect coral cores from Caribbean coral colonies. The proposed research will use multiple proxies of coral bleaching sampled in parallel down. The proposed proxies to be used in this multi-proxy approach are coral linear extension rate, skeletal density, boron isotopes, N stable isotopes and clumped isotopes.

Laboratory work will be conducted at the Universities of Glasgow Edinburgh, Southampton, and the Lyell Centre. These data will allow the scholar to generate a multiproxy reconstruction of coral bleaching, placing recent trends of coral bleaching into an environmentally relevant context.

Project Timeline

Year 1

Field work / coral collection, biogeochemical analyses

Year 2

Field work / coral collection, biogeochemical analyses, dissemination, conference

Year 3

biogeochemical analyses, conference, dissemination

Year 3.5

biogeochemical analyses, conference, dissemination

& Skills

Project support: The facilities and instrumentation available within the supervisors’ and CASE partner’s institutions provide a combination of leading laboratory, field and analytical capability and technical support that will be ideal for this proposed research, maximising PhD training from experts in the field.
Scholar support: The School of Geographical and Earth Sciences at the University of Glasgow (GES) has a large research student cohort that will provide peer-support throughout the research program. The scholar will participate in the annual post-graduate research conference within GES, providing an opportunity to present their research to postgraduates and staff within the School, and to also learn about the research conducted by their fellow postgraduate peers. All project supervisors are highly research-active; the scholar will interact with all members of their research groups, providing an opportunity to learn about other techniques and research areas which may be applicable to their research. Additionally, the supervisors are all based in research-active departments that span a broad range of ecological, environmental, genomics and bioinformatics research, exposing the scholar to a range of other research areas. To facilitate this, the scholar will actively participate in the ‘Marine Global Change Group’ in GES, the ‘Coastal Biogeochemistry’ group at the Lyell Centre, the “Changing Oceans” group and the University of Edinburgh and the “Foster Lab” at the University of Southampton. These group meetings provide opportunities to discuss cutting-edge topics in the field, review recent papers and to present current research plans to academics with a common research interest in an informal and supportive atmosphere.

The scholar will be encouraged to attend specialist courses that will directly contribute to the proposed project:
• The project involves a large component of biogeochemical research and the scholar will be encouraged to attend relevant course throughout the PhD.
• This project will involve some fieldwork, thus the scholar may attend a field first aid course in the first 6 months of the project.
• Analytical training will be provided by the supervisors and / or specialist technicians for each piece of instrumentation required for analyses.
• The project supervisors will also support and encourage the scholar’s attendance on transferable skills training such as data management, scientific writing and science communication. The Faculty of Science and Engineering at the University of Glasgow provides, for free, a large number of such courses, which are available throughout the PhD program.

References & further reading

Hughes, T. P., et al. Spatial and temporal patterns of mass bleaching of corals in the Anthropocene. Science 359: 80-83 (2018)

Hennige, S. J. et al. Acclimation and adaptation of scelractinian coral communities along environmental gradients within an Indonesian reef system. J. Exp. Mar. Biol. Ecol. 391, 143-152 (2010).

Suggett, D. J. and D. J. Smith. “Interpreting the sign of coral bleaching as friend vs. foe.” Global Change Biology 17(1): 45-55 (2011).

Kamenos, N. A. and S. J. Hennige (2018). “Reconstructing four centuries of temperature-induced coral bleaching on the Great Barrier Reef.” Frontiers in Marine Science 5: 283.

Further Information

Application procedure: For IAPETUS2 applications to the University of Glasgow please use the dedicated application portal: www.gla.ac.uk/ScholarshipApp (you will still need to submit your administrative details to the IAPETUS2 website as well).

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