Offshore wind farms threaten electro-sensitive sharks

Ongoing research into the impact of offshore wind farm electromagnetic fields (EMFs) on shark development reveals that alternating electric currents produced by underwater wind farm cables seem not to disrupt the growth or survival of sharks.

Offshore wind farms are one of the most common marine renewable energy (MRE) producers and are seen as pivotal in the global transition towards renewable energy, moving away from fossil fuels that contribute to climate change. 

However, their proliferation in marine environments raises questions about their impacts on wildlife. Researchers and energy operators are working together to understand these effects.

Wind farms and sharks

“Wind farms can induce noise, vibrations, interruptions to ecological continuity, and generate electromagnetic fields at the level of submarine electric cable,” said Julie Lucas, a research associate at France’s National Museum of Natural History. 

“They can affect the behavior of electro-sensitive species which use natural electromagnetic fields to move and feed, such as sharks.”

Submarine electric cables

These offshore wind farms rely on submarine electric cables (CES) that use either alternating current (AC) or direct current (DC), depending on their function, power output, and cable length. 

“Currently, wind farms located less than 50km from the coast use AC current, whereas more powerful future wind farms are planned to be located more than 50 km away and will use DC current,” Lucas said.

Both AC and DC currents produce strong magnetic fields in the water surrounding them. “These magnetic fields can affect the behavior of electro- and magneto-sensitive species such as elasmobranchs, which use natural electromagnetic fields to move and feed,” she explained. 

“The increasing number of offshore wind farms is likely to amplify these effects, while existing information on their impact on marine communities remains patchy.”

Potential impacts of offshore wind farms

The experts aimed to identify the effects of the magnetic fields caused by AC and DC currents on the survival, development, and behavior of sharks and other electro-sensitive elasmobranchs. 

The team studied two key life stages of the small-spotted catshark (Scyliorhinus canicular), embryo and juvenile, under either control or wind farm-impacted conditions using AC or DC currents. They recorded daily survival, weekly development and growth, and metabolic rate through respirometry for both life stages.

How sharks respond to wind farms

“Thankfully, preliminary results suggest that the impact of alternating electromagnetic fields seems to be limited to the factors that we have measured,” Lucas said. However, the full results are still being analyzed and the effects of DC current will be investigated later this year.

“The results of this project will make it possible to understand more precisely how sharks react to electromagnetic fields depending on their intensity and the type of current. They will also improve our knowledge of the impacts of MREs on marine species.”

Lucas hopes that this research can help inform policy to protect marine species and determine what improvements can be made to CES to continue limiting their impact. 

“This project will provide essential information for managers and decision-makers to meet the challenges of developing MREs without harming marine biodiversity,” she concluded.

This study is presented at the Society for Experimental Biology Annual Conference in Prague from July 2-5, 2024.

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