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

Area of Science:

• Marine Biology
• Environmental Science
• Electromagnetic Field Effects

Background:

• Subsea power cables for offshore wind farms generate electromagnetic fields (EMFs) in marine environments.
• Embryos of oviparous sharks and skates can detect EMFs, using a 'freezing response' to avoid predators.
• The impact of anthropogenic EMFs from power cables on embryonic development in these species is understudied.

Purpose of the Study:

• To investigate the behavioral responses of thornback ray (Raja clavata) embryos to varying levels of anthropogenic EMFs.
• To assess the effects of chronic EMF exposure on embryonic development, survival, and hatching in thornback rays.

Main Methods:

• Thornback ray embryos were exposed to controlled EMF levels (1.8-4.6 microT) generated by alternating current throughout their ~20-week embryogenesis.
• Behavioral parameters, including tail undulations and body movements, were monitored and compared between exposed and non-exposed groups.
• Post-hatching assessments included health, survival, development time, and biometry.

Main Results:

• Embryos chronically exposed to EMFs exhibited significantly increased activity, with 33% more tail undulations and 150% increased body movements compared to controls.
• No significant differences were found in health, survival rates after hatching, development time, or biometry between exposed and control groups.
• The 'freezing response' to EMF changes, observed in other studies, was not detected in this experiment.

Conclusions:

• Chronic EMF exposure from subsea power cables may increase the predation risk for thornback ray embryos due to heightened activity levels.
• While immediate developmental and survival impacts were not observed, potential long-term effects on hatchlings warrant further investigation.
• Further research on different species, including direct current (DC) exposure, is recommended for a comprehensive understanding of EMF effects on marine embryos.