New research reveals a compelling and previously overlooked aspect of marine biology: female common shore crabs (Carcinus maenas) exhibit a notably higher sensitivity to electromagnetic fields (EMFs) generated by underwater power cables than their male counterparts. These subsea cables, critical for powering offshore infrastructure such as wind farms, emit magnetic fields that could unintentionally influence marine life behavior and, by extension, coastal ecosystems. As offshore energy developments continue to accelerate worldwide, understanding these nuanced interactions is paramount.
The study, led by PhD researcher Elizabeth James at the University of Portsmouth’s Institute of Marine Sciences, provides some of the first empirical evidence that sex-specific behavioral changes occur in response to environmentally relevant EMF strengths, those comparable to what crabs and other marine organisms encounter naturally near submarine cables. Using a controlled laboratory environment equipped with Helmholtz coils — devices designed to generate uniform magnetic fields — the team simulated field intensities up to 3200 microteslas (μT), which encompass the range emitted by actual underwater power cables.
The researchers meticulously tracked the behavior of 120 juvenile common shore crabs, recording their spatial preferences, activity levels, and movement patterns while exposed to varying EMF strengths. It was discovered that female crabs spent significantly more time near zones with electromagnetic influence compared to non-field areas, in some cases lingering between 87% to 131% longer. Such attraction to EMFs could disrupt their natural migration routes, which are vital for reproductive cycles along coastlines.
Interestingly, male crabs displayed no significant preference for EMF-affected zones and exhibited relatively consistent movement across different field strengths. This gender disparity not only confirms the importance of analyzing sex-specific behavioral responses in marine species but also suggests an intrinsic biological difference in sensitivity or detection mechanisms. It is hypothesized that female crabs possess unique sensory abilities that make them distinctly reactive to electromagnetic variations, though the precise physiological or neurological pathways remain to be elucidated.
Beyond mere presence, the intensity of the EMFs also modulated female crab mobility. At moderate magnetic field strengths, approximately 1000 μT, female crabs reduced their movement by over a third, suggesting that EMFs may impose an inhibitory effect on their activity levels. This reduced locomotion could further compound ecological impacts, as it might delay or alter migration timing critical to successful reproduction. Even at lower intensities, under 250 μT, subtle yet measurable behavioral changes were detected.
From an ecological perspective, these findings project potentially profound consequences. Crabs are not only prolific migrators but also key players in nearshore food webs, serving as predators, prey, and scavengers. If female crabs are drawn to remain near underwater cables instead of faithfully distributing themselves along established migratory paths, it could skew population dynamics, impact egg-laying sites, and disturb predator-prey relationships. Disruptions of this nature risk cascading through marine ecosystems, especially in regions where offshore renewable energy infrastructure is densifying.
The study has broader implications for the design and placement of submarine power cables globally. While projections indicate these cables will occupy less than 0.1% of the ocean floor by 2050, localized effects on sensitive marine corridors, especially breeding grounds, could be significant. This research underscores the necessity for environmental impact assessments that integrate sex-specific responses and behavioral ecology, moving beyond assumptions that all marine animals respond identically to anthropogenic stimuli.
Professor Alex Ford of the University of Portsmouth’s School of the Environment and Life Sciences, a co-author on the study, emphasized the importance of considering sex when evaluating pollution impacts. Traditionally, in toxicology, males often appear more vulnerable because females may offload contaminants through reproduction. However, this study flips the convention, revealing females as more reactive to non-chemical pollution, tied to electromagnetic stimuli, suggesting novel sensory or physiological traits that deserve further attention.
The experimental methodology deployed advanced video tracking technology to record crab movements in 10-minute intervals, allowing precise quantification of spatial preference and mobility. The combination of Helmholtz coils’ controlled EMF generation and detailed behavioral analytics provides a robust framework to simulate realistic environmental conditions and draw ecologically relevant conclusions. This approach represents a significant advance in marine behavioral ecotoxicology.
The expansion of offshore renewable energy installations, driven by ambitious climate targets, makes this research timely and urgent. While wind farms and their associated submarine cables stand at the forefront of sustainable energy solutions, the delicate balance of marine ecosystems must not be compromised in the transition. The findings serve as a crucial reminder to policymakers, engineers, and ecologists to collaborate closely, ensuring that technological progress incorporates holistic environmental safeguards.
This investigation builds on the University of Portsmouth’s extensive track record in marine environmental research. Their prior work has shed light on the pernicious effects of plastic chemical pollutants on marine reproduction, behavioral alterations induced by contaminants, and emerging concerns about persistent substances such as per- and polyfluoroalkyl substances (PFAS). Collectively, these studies reinforce the complex ways human activity can ripple through marine life, calling for multidisciplinary strategies to protect vulnerable species.
Ultimately, the study advocates for a nuanced view of marine pollution, integrating electromagnetic pollution as an important, though less visible, stressor. It challenges the scientific community to refine assessment frameworks, considering differential sex-based impacts alongside traditional chemical and physical pollutants. By illuminating the behavioral dynamics underpinning these impacts, the research charts a path forward for minimizing unintended ecological disturbances amid the global shift to greener energy sources.
Subject of Research: Animals
Article Title: Female Crabs Are More Sensitive to Environmentally Relevant Electromagnetic Fields from Submarine Power Cables
News Publication Date: 15-Sep-2025
Web References:
- Environmental Science & Technology Letters article: http://dx.doi.org/10.1021/acs.estlett.5c00862
- University of Portsmouth Institute of Marine Sciences: https://www.port.ac.uk/about-us/our-facilities/lab-and-testing-facilities/institute-of-marine-sciences
References:
James, E., Ford, A. et al. (2025). Female Crabs Are More Sensitive to Environmentally Relevant Electromagnetic Fields from Submarine Power Cables. Environmental Science & Technology Letters. DOI: 10.1021/acs.estlett.5c00862
Image Credits: Elizabeth James
Keywords: Electromagnetic fields, Marine life, Crustacea, Submarine power cables, Behavioral ecology, Offshore renewable energy, Sex-specific response
