Learnings

Outcomes

The project has delivered a comprehensive understanding of the potential impacts of electromagnetic fields (EMFs) from high-voltage direct current (HVDC) submarine cables upon marine benthic organisms. Central to the project’s outcomes was the development of robust methods for quantifying and assessing ecologically relevant EMF levels. By examining existing HVDC systems, in particular Western Link, the project first established the typical design parameters and operational characteristics of modern subsea cable networks. By understanding the operation and electromagnetic fields at these HVDC cable systems ecologically relevant levels were modelled and decided based on fauna location. This formed the foundation for both experimental design and ecological experiments.

Building on this knowledge, within Work Package 2 a targeted meta-analysis of extant literature on EMF exposure and its effects on marine organisms was undertaken to evaluate the relevance of prior research to both HVDC and AC subsea cable systems. This literature review went beyond summarising existing studies by systematically quantifying key experimental parameters. Each study was assessed for the strength of magnetic fields tested, the species and taxonomic groups included, and the life stages examined. Outcomes were categorised into instances where measurable effects were observed versus no detectable effects. The review highlighted that benthic infauna were underrepresented in previous studies, and that many experiments exposed organisms to EMF levels higher than those likely to occur in the field or at very close proximity to cables. This structured approach allowed identification of critical knowledge gaps, contextualise the exposure scenarios most relevant to real-world cable installations, and ensure that subsequent experimental designs reflected ecologically realistic EMF conditions. Importantly, these insights informed the design of future laboratory experiments and provided stakeholders with evidence-based guidance on where uncertainties remain, and which areas require further investigation.

To be able to provide feedback and recommendations, an experimental system was developed, comprising temperature-controlled tanks containing sediment and invertebrates, alongside a cable system replicating HVDC EMF conditions (SCAMPI). Controlled exposure studies measured how behavioural and physiological responses differed between key sediment invertebrate species and across different EMF scenarios, generating high-quality, repeatable data. This work led to a peer-reviewed conference publication documenting the experimental approach and providing a replicable framework for assessing EMF impacts on benthic infauna (Rzempoluch et al., 2025). The paper also validated EMF measurement and modelling protocols, advancing the Technology Readiness Level from proof-of-concept to validated application in relevant marine environments. This methodological paper was developed to support future EMF research on marine organisms and is relevant both to investigations focussing on benthic and pelagic impacts.

Building on the methodological framework established in the earlier publication, Work Package 4 applied these approaches to directly test whether EMFs from HVDC cables caused measurable behavioural and physiological changes in benthic invertebrates, examining the effects of exposure duration related to variations in demand, seasonal variations, and species-specific differences. Work Package 5 Experimental findings were consolidated, to provide guidance on EMF impacts and demonstrate the practical application of the methods. This ensured that the project not only generated robust, high-quality scientific evidence but also translated these findings into practical insights for industry, supporting interpretation of existing literature and informing considerations for future submarine cable projects, including installations such as the Eastern Link and Southeast HVDC projects.

The project has provided high-quality research where significant uncertainty previously existed and has resulted in short- and long-term recommendations to improve and standardise research, promote data sharing, and guide future studies on species-specific sensitivity and long-term ecological effects. In doing so, it ensures that environmental impacts of marine projects are adequately addressed while supporting the transition to Net Zero through responsible offshore HVDC development.

Future project 1) Field-based biodiversity assessment near cables
A valuable next step would be to collect sediment cores at varying distances from existing HVDC cables to assess whether biodiversity, species abundance, or community composition changes with proximity to EMF sources. This would provide real-world context to laboratory findings and help determine whether long-term exposure leads to migration, avoidance, or alterations in benthic community structure. Such data would address current gaps in understanding species distributions near operational cables and support evidence-based environmental assessments. 

Future project 2) Community-level experiments
Future research could examine mixed-species communities rather than single-species cores. Interactions between species may mitigate or amplify individual responses to EMFs. For example, if one species increases burrowing while another decreases it under the same exposure, the net effect on wider sediment dynamics may be negligible. Community-level experiments would therefore provide a more ecologically realistic assessment of EMF impacts and better inform ecosystem-level risk evaluations.

Lessons Learnt

The project initially was structured as a sequential programme progressing from engineering system understanding, through literature review, to experimental construction and biological testing, before concluding with dissemination and guidance development. In practice, one of the key lessons learned is that EMF-related environmental research cannot be delivered effectively through a strictly linear workflow. Greater value was achieved through iterative integration between work packages, particularly between HVDC system parameter definition, literature gap analysis, and experimental design. Translating cable engineering characteristics (e.g., load profiles, burial depth, installation conditions and DC configuration) into defined and replicable ecological exposure scenarios required more detailed technical alignment than originally anticipated. This highlighted the importance of early and continuous collaboration between engineering, environmental and research teams in future projects to ensure modelling assumptions and ecological testing are directly comparable.                                                                                                                                                  

The literature review (WP 2) provided critical methodological and strategic insight beyond initial expectations. The review systematically examined both AC and DC exposure studies across different species groups and EMF intensities, while also categorising reported outcomes (e.g., no observable effect, behavioural response, physiological impact). This enabled quantification of the exposure ranges that have been tested for different taxa and highlighted substantial variability in experimental design and reporting standards. Importantly, the review did not simply summarise findings but identified clear evidence gaps, including taxonomic biases and under-representation of certain ecological receptors. Benthic invertebrates were identified as a particularly understudied group despite their high likelihood of interaction with buried HVDC cables. The analysis also clarified where experimental exposure levels did not align well with realistic subsea cable emission scenarios, indicating a disconnect between laboratory research and installation conditions. This evidence-mapping approach provided a clearer basis for targeting future experimental work, ensuring that subsequent testing focused on ecologically relevant species groups and realistic EMF exposure ranges. For future projects, undertaking this type of structured exposure-and-effect mapping at an early stage would enable more strategic prioritisation of research effort and strengthen the defensibility of consenting assessments.

The development of the experimental EMF system (WP1, WP3, WP4) provided important methodological insight, particularly regarding the importance of scenario-based planning. While the laboratory platform was successfully constructed to replicate realistic HVDC emission conditions, it became clear that EMF exposure cannot be meaningfully assessed in isolation from location and ecological context. For example, EMF profiles associated with buried HVDC cables differ materially from those of exposed infrastructure, and the relevance of these fields varies depending on receptor type (e.g., mobile fish species versus benthic invertebrates), behavioural state, season, and time of day. As a result, the experimental design was refined to investigate both EMF strength under different seasonal contexts, and different EMF duration intervals based on variations in demand rather than differences in EMF intensity. This approach ensured that exposure gradients, sediment conditions and seasonal variables were aligned with realistic cable scenarios. The key lesson for future projects is that EMF research should be structured around clearly defined infrastructure and ecological scenarios from the outset, ensuring that modelling assumptions, biological endpoints and environmental variables reflect ecologically relevant scenarios that rather than focussing on worst-case scenarios that may only be experience for very short periods of time (hours). Embedding scenario-based planning into experimental designs strengthens regulatory relevance and improves confidence when translating modelling outputs into ecological risk interpretation.