Quantifying the impacts of polyaromatic hydrocarbons (PAHs) from infrastructure decommissioning on benthic micro and macrofaunal communities

Master’s by Dissertation (MSD) project: Quantifying the impacts of polyaromatic hydrocarbons (PAHs) from infrastructure decommissioning on benthic micro and macrofaunal communities

Summary: In the North Sea, there are >1,500 offshore oil and gas (O&G) installations. Current environmental regulations prohibit leaving any installations in place, under OSPAR Decision 98/3, which means all infrastructure must be removed when production ceases. However, a considerable number of O&G installations, particularly those installed before the 1998 OSPAR regulations, were not designed with full removal in mind, meaning partial removal and derogation is the only option during decommissioning. Previous studies have shown partial removal and derogation enhances the biodiversity of marine biota growing on the remaining structures, which may in turn alter the sediment nutrient chemistry (Klunder et al., 2020). Additionally, the O&G extraction activities may influence local sediment biodiversity in response to contaminants released (e.g. hydrocarbons) (Laroche et al., 2018; Potts et al., 2019). Currently, there is a lack of knowledge on how infrastructure decommissioning shapes benthic microbial and macrofaunal biodiversity and in turn how this affects ecosystem function (e.g. hydrocarbon biodegradation). Such information is crucial for stakeholders when deciding on appropriate decommissioning scenarios.

Committed academic support: This project takes advantage of existing archived benthic sediment samples collected along a distance gradient from 50 m to 3200 m away from two North Sea platforms (i.e. North West Hutton and Miller, that were decommissioned in 2009 and 2018 respectively). The University of Essex has obtained a suite of hydrocarbon data (petroleum alkanes, PAHs), archived DNA and metagenome data from these sediments that will be made available to the student. All supervisors have well-established track records of supervising Masters and PhD students to completion and are fully committed to supporting the student. Therefore this project is very low risk.

Aims: The overarching aim of this project is to quantify the impact of PAHs from decommissioned infrastructure on sediment microbial and macrofaunal communities.

Objectives:

1. Data mine hydrocarbon data to characterise PAH classes/concentration in sediments.
2. Data mine metagenome library to identify key PAH-degrading microbial genes.
3. Quantify key PAH-degrading gene abundance using qPCR to determine how PAH degradation potential of these sediments changes following decommissioning.
4. Use metagenome data and eDNA approaches to characterise and quantify benthic macrofaunal communities and relate to sediment, PAH and nutrient concentration.
5. Based on the PAH data analysis (from Obj 1) establish microbial biodegradation microcosm experiments targeting a range of PAHs (concentration/ compound) and relate to changes in community and functional gene diversity.
6. Data analysis, paper/ thesis writing.

Student training: The project combines analytical chemistry, bioinformatics and molecular microbial/macrofaunal ecology. The student will gain broad skills in hydrocarbon (PAH) analysis, metagenomics. lab experiments, data analysis, report writing and opportunities to give scientific presentations at UK/international conferences.

Deadline for applications 1^st Feb 2026

Apply with a CV and cover letter to lspgrapplications@essex.ac.uk–