The volatile nature of tropical reef ecosystems in a changing world

Biogeochemical Cycles



Tropical coastal ecosystems are some of the most diverse and productive on Earth. They are also significant producers of biogenic volatile organic compounds (BVOCs), volatile chemicals with key ecophysiological functions, major roles global biogeochemical cycling of elements and a role in local-regional climate regulation. Understanding BVOC dynamics, and drivers of variability is therefore crucial for predicting how these ecosystems may respond to projected climate change (e.g. warming, acidification and changes to ecosystem structure).

Dimethylsulphide (DMS) and isoprene are two of the most abundant BVOCs, respectively responsible for the ‘smell of the sea’, ‘blue haze’, observed in forested mountains. In tropical reef systems, the land-sea ecosystem transition (i.e. mangroves to coral reefs) results in a BVOC continuum. However, our understanding of BVOC dynamics and their role in local-regional biogeochemical cycling is limited, preventing us from incorporating this crucial ecosystem feature into conservation and management plans.

The aim of this project is to quantify the natural dynamics of this BVOC continuum, using compound-specific quantification and isotopic differentiation to identify the sources and sinks of isoprene and DMS within the mangrove-seagrass-coral reef system. Field studies conducted on Caribbean reefs (including Honduras, Dominica) and lab-based aquarium experiments will enable the environmental and biological drivers of BVOC variability to be determined, allowing projections for future BVOC signatures to be estimated.

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Image Captions

Picture 3.jpg: The transition from land to sea around coral reefs presents a fascinating and uncharted biogeochemical system [credit: Erik Lukas / Coral Reef Image Bank]

Picture 2.jpg: Coral and algal sampling on a coral reef by one of the project supervisors [credit: Nick Kamenos]


The PhD student will have the opportunity to collect samples from mangrove forests, seagrass meadows and coral reefs from multiple sites within the Caribbean (SCUBA diving is optional) for BVOC quantification. In situ experiments (e.g. herbivore exclusion and macrophyte removal plots) will enable biological and environmental BVOC drivers to be identified. BVOCs will be quantified using gas chromatography and their potential sources identified using state-of-the-art compound-specific isotope analyses, using facilities available at the Lyell Centre. This could be conducted in the laboratory and supplemented by the considerable volume of historical biodiversity data available from Operation Wallacea, should Covid-19 travel restrictions still be in place. 3D modelling of the ecosystem will enable biogeochemical results to be scaled up to the coverage of local management boundaries; comparison to historical survey records will indicate how BVOC biogeochemistry has been impacted by human disturbance. Further mechanistic insight will be gained via the opportunity to conduct multifactorial laboratory aquarium experiments under highly controlled conditions of light, temperature, nutrients and carbon chemistry, using state-of-the-art facilities available within the Lyell Centre research aquarium. Climate change experiments and modelling (based on IPCC projections) will enable the scholar to project how BVOC dynamics will likely change over the coming decades, and identify how this may impact future ecosystem function.

Project Timeline

Year 1

Literature review, field & analytical technique development, summer fieldwork

Year 2

Sample analysis & interpretation, laboratory experiments, summer fieldwork, presentation at a national conference

Year 3

Sample analysis & interpretation, write-up for publication, presentation at an international conference

Year 3.5

Writing-up of results and completion of thesis, submission of papers for publication

& Skills

Project support

The facilities, equipment and expertise available within the institutions and supervisory team provide a combination of world-leading field, analytical and laboratory capability and technical support that ideally fits this PhD project, maximising the expert training that will be available.

This project will equip the student with a range of skills, including fieldwork, analytical science, numeracy and translation of science for wider audiences. Specific research skills will include:
– Gas chromatography
– Compound-specific stable isotope analyses
– 3D coral reef modelling
– Coastal marine fieldwork
– Invertebrate and algal culturing and husbandry
– Experimental design
– Environmental statistics

PhD student support

The Lyell Centre has a large research student cohort that will provide peer-support throughout the studentship, including participation in the annual post-graduate research conference. All project supervisors are also highly research-active. The PhD student will interact with all members of their research groups through lab-group meetings at the Lyell Centre, University of Glasgow and Operation Wallacea, 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 and geoscience research, exposing the scholar to a range of other research areas. Active participation in these research groups will provide the opportunity 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 PhD student will also have the opportunity to undertake a placement with Operation Wallacea, providing work experience within a non-academic organisation.

Where required, and to maintain continued professional development, the PhD student will be supported to attend specialist courses directly aligned to the project:
– Stable isotope mass spectrometry
– Spatial statistics
– Possibly a field first aid course in the first 6 months of the project.
– Possibly scientific diving courses
– Analytical training for each piece of instrumentation required for analyses.
– Attendance to transferable skills training such as data management, scientific writing and science communication. These are provided for free within Heriot-Watt University’s Research Futures Academy.

References & further reading

Exton, D.A. et al 2015. Uncovering the volatile nature of tropical coastal marine ecosystems in a changing world. Global Change Biology, 21(4), 1383-1394.

Burdett, H. L. et al 2013. Spatiotemporal variability of dimethylsulphoniopropionate on a fringing coral reef: the role of reefal carbonate chemistry and environmental variability. Plos one, 8(5), e64651.

Jackson, R. L. et al (2020). Coral reefs as a source of climate-active aerosols. PeerJ, 8, e10023.

Further Information

In the first instance, enquiries should be directed to the primary supervisor, Dr Heidi Burdett ( Please indicate why you are interested in this project and attach your CV to the email.

For eligible candidates, funding is available to cover tuition fees, stipend and research costs. However, please note that this project is in competition with others for funding, and success will depend on the quality of applications received.

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