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Impacts of anthropogenic disturbance on seabed functioning

   School of Energy, Geoscience, Infrastructure and Society

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  Dr Marija Sciberra  No more applications being accepted  Funded PhD Project (Students Worldwide)

Edinburgh United Kingdom Climate Science Data Analysis Ecology Geochemistry Marine Biology Geography Statistics Zoology

About the Project

Over the last century, the use of bottom trawls and other mobile fishing gears have increased in intensity and geographic extent. Through contact with the sea floor, these gears can significantly modify benthic habitats and their associated benthic communities, which in turn can lead to concomitant effects on biogeochemical cycles and other important ecosystem processes and functions of global importance. For example, biogeochemical alterations impact the capacity of the sediment to recycle organic matter back to bioavailable nutrients. To date there is only limited information about the impact of fisheries on the marine nutrient cycling and organic carbon mineralization, and knowledge of the cumulative effects of trawling and other anthropogenic disturbances such as climate change and hypoxia on seabed functioning is even more lacking.

This studentship will combine existing spatiotemporal datasets of benthic faunal, geochemical and physical data from the North Sea to conduct a quantitative assessment of the relationship between species functional traits and biogeochemical process rates (e.g. oxygen consumption and nutrient fluxes) known to influence wider ecosystem properties. The student will use meta-analysis to quantify trawling impact (in terms of biomass loss and recovery rates) on species functional traits identified as correlates for biogeochemical processes. Biogeochemical modelling using a 1D dynamic diagenetic model will then be used to assess the loss of macrofauna biomass and species functional traits on nutrient cycling and organic carbon mineralization. The model will also be used to study the combined effects of bottom trawling, hypoxia and temperature on the biogeochemical dynamics of seabed habitats which are becoming increasingly important to consider as interactions between trawling, climate change and oxygen limitation on marine ecosystems are expected to increase in many areas worldwide that are typically important fishing grounds.

This PhD provides an opportunity for important research to be undertaken to build a more concrete knowledge base on the ways fisheries interact with global biogeochemical cycles. The student will have the opportunity to develop skills in trait-based approaches, biogeochemical modelling, evidence synthesis tools and meta-analysis. Although the PhD is primarily a desk-based project using existing datasets, there might be an opportunity for the student to participate in collaborative fieldwork at sea on board a research vessel and receive training in the sampling methodologies and survey techniques used to collect faunal and biogeochemical data. The student will have opportunities to develop science communication skills through participation in international or national conferences, and presentation of research during seminars held at HWU, BU, NIOZ and CEFAS. There will also be an opportunity to participate in the ICES working group on Fisheries Benthic Impacts and Trade-offs (WG FBIT) that brings together a multidisciplinary group of scientists from more than 15 countries to advance assessment methods of trawling impacts on benthic marine communities and their functioning.


Applicants are requested to send a cover letter stating why they are interested in the PhD, what ideas you could bring to the project, and outline any relevant experience. Please also submit a CV with all qualifications to date. The cover letter and CV should be sent to Dr Marija Sciberras ([Email Address Removed]). Candidates are invited to contact Dr Sciberras for an informal discussion about the project.

In addition, to apply you must complete our online application form. Please select PhD programme Marine Biology and include the full project title, reference number and supervisor (Dr M Sciberras) on your application form. Ensure that all fields marked as 'required' are complete. You must complete the section marked project proposal; upload a supporting statement/cover letter documenting your reasons for applying to this particular PhD project, why you are an ideal candidate for the position and what ideas you could bring to the project. You will also need to provide a CV, a copy of your degree certificate/s and relevant transcripts. You will be asked to enter details of an academic referee who will be able to provide a technical reference. You should ask your referee to upload their reference letter by the closing date of this advert - until your nominated referee has uploaded their statement, your application will not be marked as complete and will not be considered by the review panel. You must also provide proof of your ability in the English language (if English is not your mother tongue or if you have not already studied for a degree that was taught in English within the last 2 years). We require an IELTS certificate showing an overall score of at least 6.5 with no component scoring less than 6.0 or a TOEFL certificate with a minimum score of 90 points.

Please contact Dr Marija Sciberras ([Email Address Removed]) for further information or an informal discussion.

Funding Notes

This is a full scholarship, funded for 3 years and covers the PhD tuition fees and stipend (currently £15 285 per annum), covered by Heriot-Watt University. Full funding is available to UK, EU and international students.


De Borger E, Tiano J, Braeckman U, Rijnsdorp AD, Soetaert K. 2021. Impact of bottom trawling on sediment biogeochemistry: a modelling approach. Biogeosciences.
Hiddink JG, Jennings S, Sciberras M, et al. 2018. Assessing bottom-trawling impacts based on the longevity of benthic invertebrates. Journal of Applied Ecology.
Rijnsdorp AD, Bolam SG, Garcia C, Hiddink JG, et al. 2018. Estimating sensitivity of seabed habitats to disturbance by bottom trawling based on the longevity of benthic fauna. Ecological Applications.
Toussaint E, De Borger E. Braeckman U et al. 2021. Faunal and environmental drivers of carbon and nitrogen cycling along a permeability gradient in shallow North Sea sediments. Science of the Total Environment.
Sciberras M, Hiddink JG, Jennings S, et al. 2018. Response of benthic fauna to experimental bottom fishing: a global meta-analysis. Fish and Fisheries.
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