An egg case study: Chronic exposure to AC electromagnetic fields results in hyperactivity in thornback ray (Raja clavata L.) embryos.

Abstract

Subsea power cables, required for offshore generated wind power transport, emit electromagnetic fields (EMFs) into the marine environment. EMFs also occur naturally, resulting from biotic (animals) and abiotic (geomagnetic field) sources. Skate and oviparous shark embryos in the egg can sense EMF from predators and respond by reducing their normal movement ('freezing response') to prevent detection and subsequent predation. When nursery areas overlap with power cables, embryos will be exposed to varying levels of anthropogenic EMFs and effects thereof on embryonic development is currently understudied. Here, we present behavioral responses of thornback ray (Raja clavata) embryos to varying field-related EMF levels (1.8-4.6 μT) generated by alternating current throughout embryogenesis (∼20 weeks). Chronically exposed individuals were overall more active, including 33 % more tail undulations and 150 % increased body movements, compared to non-exposed individuals. This increased activity suggests that eggs exposed to EMFs generated by subsea power cables might be at risk of increased predation. We found no indications of reduced health or survival after hatching, or changes in development time or biometry. Effects on subsequent life stages cannot be excluded, follow-up studies should observe hatchling development. We did not observe an increase in freezing response resulting from EMF change as described by other researchers who used different types and intensities of EMF cues. We recommend that different species, along with DC exposure, should be studied to gain a more complete insight into the potential effects of EMF exposure during embryogenesis of these EMF-sensitive species.

AI evidence extraction

Main findings

Thornback ray embryos chronically exposed to AC EMFs (1.8–4.6 μT) throughout embryogenesis (~20 weeks) were overall more active than non-exposed embryos, with 33% more tail undulations and 150% increased body movements. No indications of reduced health or survival after hatching, and no changes in development time or biometry, were reported. No increase in freezing response due to EMF change was observed.

Outcomes measured

• Embryo activity/behavior (tail undulations, body movements)
• Freezing response to EMF change
• Health/survival after hatching
• Development time
• Biometry

Limitations

• Sample size not reported in the provided abstract/metadata
• Only behavioral and early post-hatching endpoints reported; effects on subsequent life stages not assessed
• Exposure described as AC EMF levels (μT) without additional exposure characterization (e.g., frequency details) in the provided abstract
• Single species studied; authors recommend additional species and DC exposure studies

Suggested hubs

• occupational-exposure (0)

{
    "study_type": "animal",
    "exposure": {
        "band": "ELF",
        "source": "subsea power cables (alternating current)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "chronic exposure throughout embryogenesis (~20 weeks)"
    },
    "population": "Thornback ray (Raja clavata L.) embryos (in egg cases)",
    "sample_size": null,
    "outcomes": [
        "Embryo activity/behavior (tail undulations, body movements)",
        "Freezing response to EMF change",
        "Health/survival after hatching",
        "Development time",
        "Biometry"
    ],
    "main_findings": "Thornback ray embryos chronically exposed to AC EMFs (1.8–4.6 μT) throughout embryogenesis (~20 weeks) were overall more active than non-exposed embryos, with 33% more tail undulations and 150% increased body movements. No indications of reduced health or survival after hatching, and no changes in development time or biometry, were reported. No increase in freezing response due to EMF change was observed.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in the provided abstract/metadata",
        "Only behavioral and early post-hatching endpoints reported; effects on subsequent life stages not assessed",
        "Exposure described as AC EMF levels (μT) without additional exposure characterization (e.g., frequency details) in the provided abstract",
        "Single species studied; authors recommend additional species and DC exposure studies"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "subsea power cables",
        "offshore wind",
        "alternating current",
        "electromagnetic fields",
        "ELF magnetic field",
        "marine environment",
        "ray",
        "Raja clavata",
        "embryogenesis",
        "egg case",
        "behavior",
        "hyperactivity",
        "predation risk"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0,
            "reason": null
        }
    ]
}

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