Investigating environmental contaminants in Flapper skate egg cases

Elasmobranchs are among the most threatened marine organisms globally (Dulvy et al. 2014), subject to multiple anthropogenic pressures including mortality through commercial fisheries, habitat destruction, and pollution, against a background of advancing climate change. Due to these species’ ecological role as predators, bioaccumulation of contaminants through their diet can be a significant threat to their health (e.g., Weijs et al. 2015; Torres et al.2016), but other pathways of exposure also exist. For egg-laying sharks and rays, one such pathway involves the embryonic stage, which in larger species can take >1 year to develop and hatch (Benjamins et al. 2021), during which time the egg cases remain stationary and exposed to water-borne environmental contaminants. Previous experimental studies have highlighted the potential for a range of contaminants to accumulate onto the egg case (Jeffree et al 2006, 2007), with possible negative health impacts that can influence long-term population persistence. Long-term comprehensive conservation frameworks for sharks and rays need to consider environmental pollution risks.

One species of particular conservation interest is the Flapper skate (Dipturus intermedius). Once common throughout northwest European shelf waters, it has been severely impacted by commercial fishing and is now considered Critically Endangered by the IUCN (Ellis et al. 2024). Scottish waters appear a remaining stronghold for the species, which is listed as a Priority Marine Feature by the Scottish government. To date, limited knowledge is available about hazards posed by contaminants to this species, which is not generally maintained in captivity. While few egg nursery sites have been identified to date (Dodd et al. 2022), evidence of reproduction is provided by presence of spent egg cases on beaches, particularly in Orkney (Scotland, UK). These cases offer opportunities for understanding risks posed by accumulated contaminants to developing embryos.

The proposed project will analyse beach-cast flapper skate egg cases from Orkney (and potentially elsewhere in Scotland) for the presence and concentration of multiple different contaminants (metals, polyaromatic hydrocarbons, pharmaceuticals etc.), and put these findings into a broader context based on the wider scientific literature, to evaluate potential health risks on developing skate embryos and any subsequent population-level consequences. This will involve analyses of Flapper skate spent egg cases using inductively-coupled plasma mass spectrometry (ICP-MS), high performance liquid chromatography, and other analytical chemistry techniques. This MRes project is intended to start in October 2025 and run for 1 year, during which time the student will evaluate heterogeneity in contaminant loads within and among egg cases of known collection date/location, to develop a Standard Operating Procedure for analysing egg case contaminant loads. Measured contaminants will be compiled to provide an extensive dataset on pollution load within the egg cases, and levels will be compared against literature values and published environmental quality standards. Finally, pollution risk will be evaluated by assessing the combined levels against literature assessments of contaminant harm (focusing on elasmobranch and fish studies), and guidelines will be written highlighting any groups of contaminant compounds of particular high risk.

The project will enhance our understanding of contaminant concentrations in egg cases of flapper skate, and thereby allow us to understand the risks to long-term health posed by extended exposure to anthropogenic pollutants concentrated through accumulation into the egg case. This information will underpin subsequent conservation and management efforts for this and other species of elasmobranchs in Scotland and worldwide. The project would suit a candidate with analytical chemistry and laboratory skills and who seeks to contribute to applied marine conservation using analytical environmental chemistry tools.

References: Benjamins, S., et al.. (2021). Journal of Fish Biology, 99(3), 1150-1154. Dodd, J., et at. (2022). Aquatic Conservation: Marine and Freshwater Ecosystems, 32(10), 1647-1659. Dulvy, N. K., et al. (2014). elife, 3, e00590.  Ellis, J.R., et al. (2024). Dipturus intermedius (amended version of 2021 assessment). The IUCN Red List of Threatened Species 2024: e.T18903491A256581177. https://dx.doi.org/10.2305/IUCN.UK.2024-1.RLTS.T18903491A256581177.en. Accessed on 12 May 2025.Torres, P., et al. (2016). Science of the Total Environment, 573, 1021-1030.Weijs, L., et al. (2015). Environmental research, 137, 199-207.

Director of Studies:  Dr Steven Benjamins.

Supervisory Team: Dr Helena Reinardy.

Course Start Date: 1^st October 2025.

Funding: This 12 month MRes is self-funded.