Genetic mechanisms for acclimation and adaption to coral bleaching

Overview

The ecosystem services provided by coral reefs are worth over $100 billion annually and include coast line protection, tourism, food and medical derivatives. However, the health of the constituent corals can be significantly impacted by coral bleaching. Coral bleaching 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. This may form the basis for adaptive and acclimatory capacity to warming in corals.
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 their ability to survive bleaching at centennial time scales through acclimatisation and adaptation processes. However, we now have historic bleaching records that extend over the last 400 centuries (Kamenos and Hennige, 2018). While these records indicate corals may be reaching a tipping point in terms of survivability, the records also show evidence for periods of coral acclimatisation in the past, likely driven by key features of the coral holobiont (i.e. the coral and all associated symbionts and microbes).
To understand the relevance of current bleaching trajectories and the likelihood of future coral acclimation and adaptation, records of past acclimation and adaption by the coral holobiont are needed.

Aim: This project will determine past acclimation and adaptation of the coral holobiont to environmental change. This is important as it will enable a more robust understanding of coral survival under global change.

Click on an image to expand

Image Captions

Figure 1: Before and after widespread bleaching of a Samoan coral reef (Photo: The Ocean Agency / XL Catlin Seaview Survey)

Figure 2: Differing trajectories of historic coral bleaching frequency and prevalence on the Great Barrier Reef

Figure 3: The supervisory team extracting a coral core

Methodology

The scholar will have the opportunity to collect coral cores from Caribbean coral colonies (Fig. 3; diving is optional) from field sites in Honduras and/or Dominica. The focus of this project will be genomic analysis and interpretation. Analyses will involve Next Generation Sequencing, bioinformatic analysis and subsequent interpretation in the context of environmental change (e.g. Stat et al, Arif et al.). Laboratory work will be conducted at the University of Glasgow and the Lyell Centre. These data will allow the scholar to determine if centennial-scale acclimatisation or adaptation has previously occurred, placing recent trends of coral bleaching into an environmentally relevant context.

Project Timeline

Year 1

Collection of coral cores (field work), growth band analysis, genomic analysis

Year 2

Continuation of genomic analysis, bioinformatics, paper writting and dissemination

Year 3

Continuation of genomic analysis, bioinformatics, paper/chapter writting and dissemination, confernce attendance

Year 3.5

Completion of PhD write up, dissemination

Training
& Skills

Project support: The facilities and instrumentation available within the supervisors’ and CASE partner’s institutions provide a combination of internationally 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. 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 genomic 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).

Hoegh-Guldberg, O. et al. Coral reefs under rapid climate change and ocean acidification. Science 318, 1737-1742, doi:10.1126/science.1152509 (2007).

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).

Stat, M., Morris, E. & Gates, R. D. Functional diversity in coral-dinoflagellate symbiosis. Proc. Natl. Acad. Sci. U. S. A. 105, 9256-9261, doi:DOI 10.1073/pnas.0801328105 (2008).

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.

Arif, C. et al. Assessing Symbiodinium diversity in scleractinian corals via next-generation sequencing-based genotyping of the ITS2 rDNA region. Molecular Ecology 23, 4418-4433 (2014).

Further Information

Please contact Nick (nick.kamenos@glasgow.ac.uk) before applying

 

IAPETUS applications: to apply for this PhD please use the url: https://www.gla.ac.uk/study/applyonline/?CAREER=PGR&PLAN_CODES=CF18-7316

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