Sharks, rays, lobsters affected by underwater electric cables

            Little is known about how marine life will respond to the electromagnetic fields emanating from the spiderweb of cables carrying electricity from the Block Island Wind Farm and the many other offshore wind power installations planned for the East Coast. But a new series of studies by a team of oceanographers at the University of Rhode Island suggests that some organisms will definitely be affected.

            “The concern is that DC currents generate permanent electromagnetic fields, and we don’t really know how organisms will relate to them,” said John King, a professor at URI’s Graduate School of Oceanography. “We know that some organisms, like sharks and skates, are sensitive to these things. So the question becomes, if you build offshore power facilities, will

migratory organisms cross the cables or not. Will it affect eels that migrate to the Sargasso Sea or lobsters that have an onshore-offshore annual migration?”

            To find out, King and postdoctoral research fellow Zoe Hutchison conducted a series of field experiments around the Cross Sound Cable that carries electricity from New Haven to Long Island. They attached acoustic tags to skates and lobsters and placed them in an enclosure around the cable. An array of hydrophones in the enclosure detected the animals’ movements. Additional animals were placed in a second enclosure farther from the cable to compare the results.

            “We definitely saw effects in behavior in both lobsters and skates, though it was more dramatic in the skates,” said King, who serves on the Rhode Island Coastal Resources Management Council’s Habitat Advisory Board for offshore wind development. “The skates liked to spend time in the areas that had the highest EMFs. Their swimming behavior was definitely altered as they approached the cable. We didn’t see any evidence that a single cable is a migratory barrier, but they could definitely detect it and reacted to it.”

            “The skates moved slower around the cable but also moved more often and covered a longer distance,” added Hutchison. “They did a lot more turning, like an exploratory behavior, as if they were looking for food.”

            Sharks and skates have a sensory ability to detect the electromagnetic fields generated by the circulatory system of their prey, according to King, and they may also use it to find mates.

            “They might think the cable indicates a food source, so they spent time around the cable thinking they’re going to get fed,” he said.

            The experiment found that lobsters moved less freely around the cable, but the electromagnetic fields did not prevent them from crossing it.

            “The lobster response was much more subtle than the skates,” Hutchison said. “They had an increased exploratory behavior, too, but it wasn’t as pronounced as the skates. We know that spiny lobsters in the Caribbean use the Earth’s magnetic field to orient themselves and to figure out where to go, so we postulate that American lobsters may have a similar ability to detect magnetic fields.”

            King and Hutchison will conduct a similar study with migratory eels this fall to assess how they are affected by the cables. (They attempted it last year, but little electricity was traveling through the cable at the time.) Rather than placing the eels in an enclosure around the cable like they did with the skates and lobsters, they will release tagged eels to see how they behave as they cross the cable on their way to the Sargasso Sea, where they spawn.

            “Previous studies have shown that eels slow down and investigate every cable they cross. One study found that when eels had to cross multiple cables, they slowed down every time,” said King. “So we wonder if they have a whole bunch of cables to cross, does it slow them down enough that they never get to the Sargasso Sea.”

            The researchers pointed out that just because the behavior of the animals they tested was affected by the cables, it does not necessarily mean they were negatively impacted by them. They are, however, worried about the cumulative impacts of the electromagnetic fields from the numerous cables that will likely be installed for many offshore wind turbines in the future.

            “There’s going to be hundreds or thousands of turbines off the East Coast, so it would be nice to understand these effects and how it translates into impacts before they get built,” King said. “Right now the government is pushing full speed ahead to get these things built, and I don’t think they really care that much about their impacts. The environmental reviews are being done really fast.”

            King is also worried that the results of his studies are being downplayed by the Bureau of Ocean Energy Management, which funded the research, due to political pressure.

            “They hired a consulting company to produce a public document about our studies, and they minimized EMF as a concern and misinterpreted our study,” he said. “We didn’t say that we saw something that needed to be addressed immediately, but we also didn’t say that what we saw is OK and not to worry about it.”

            King believes more studies need to be done before any conclusions can be drawn about the effect of electromagnetic fields from power cables on marine life.

            “From a marine spatial planning context, it probably makes sense to have cable corridors rather than randomly distribute the cables all over, and that would probably have different results than studies of just a single cable. So we still have some questions to answer.”

This article first appeared in EcoRI.org on Sept. 11, 2019.