Shockwaves Beneath the Waves: How Underwater Cables Are Disrupting Crab Behaviour

As the world eagerly constructs greener energy infrastructure, a less noticed ecological narrative is emerging on the ocean floor. From the North Sea to the Bay of Bengal, scientists have found that electromagnetic fields (EMFs) emitted by underwater power cables—used to connect offshore wind farms and data networks—might be impacting one of the ocean’s most resilient creatures: crabs.

Recent research indicates that brown crabs (Cancer pagurus) and other benthic species are unusually sensitive to electromagnetic fields produced by the high-voltage direct current (HVDC) cables that span coastal waters. These cables carry electricity from offshore turbines to the mainland, creating invisible electromagnetic “halos” that extend several meters around them.

In controlled experiments, researchers observed that crabs exposed to EMFs exhibited altered activity patterns. Instead of foraging or moving freely, they often became sluggish and tended to gather directly over the cables, apparently drawn to the magnetic fields. Over time, this behavior could have serious consequences. “Crabs use magnetic cues to navigate, find food, and even select mating grounds,” explained Dr. Suresh Karunaratne, a marine ecologist studying the phenomenon off Sri Lanka’s western coast. “Disrupting those signals may affect their natural cycles and, ultimately, their population health.”

The potential implications extend beyond individual species. Crabs play a crucial role in marine ecosystems as both predators and scavengers, recycling nutrients and maintaining seabed balance. If electromagnetic interference alters their distribution or reproduction, entire food webs could be affected. Fishermen have already begun noticing changes. “We used to see steady catches along the same rocky stretches,” said a fisherman from Galle. “Now the crabs seem to move unpredictably.”

However, scientists urge caution before making sweeping conclusions. EMF exposure levels vary depending on cable design, current load, and seabed composition. Some researchers argue that with better shielding and careful routing, the risks can be minimized. Industry groups have started funding long-term monitoring programs to better understand and mitigate potential effects.

The debate highlights a broader challenge of the renewable energy transition: balancing technological progress with ecological responsibility. As nations rush to expand offshore wind capacity and undersea data links, the unseen consequences of electromagnetic pollution must be part of the discussion.

Ultimately, the story of crabs and underwater cables serves as a reminder that even the cleanest technologies can have unexpected effects on the natural world. The task ahead is to ensure that the quiet hum of human progress does not drown out the delicate rhythms of life beneath the waves.