Wind Turbines: Hearing of UK Harbor Seals May be At Risk

Scientists are still working to figure out how various noise pollution affects marine animals, and now new research suggests that the building of wind turbines may be putting the hearing of UK harbor seals at risk.

There are currently 1,184 offshore wind turbines located along the coast of the United Kingdom, collectively generating around 4GW of power. And last year, construction began on hundreds more turbines, the impact of which on sea mammals is still widely unknown.

To figure out if nearby seals' hearing may be hurt as a consequence, a team of ecologists from the University of St Andrews attached GPS data loggers to 24 harbor seals while offshore wind turbines were being installed back in 2012. They collected data on the seals' locations and their diving behavior, comparing it with noise from pile driving during wind turbine construction.

Offshore wind turbines are installed using pile drivers - essentially large hammers that drive the foundation posts into the seabed - which produce short pulsed sounds every few seconds.

"These are some of the most powerful man-made sounds produced underwater, noise capable of travelling large distances underwater," lead study author Dr. Gordon Hastie said in a statement.

According to the study results, half of the tagged seals were exposed to noise levels that exceeded hearing damage thresholds.

"Like most marine mammals, harbor seals have very sensitive underwater hearing at a much broader range of frequencies than humans," Hastie said. "Seals probably use underwater hearing during the mating season and to detect and avoid predators. They may also rely on their hearing for navigation and finding prey."

These findings could have potential important implications, as seals are protected under European law, and the construction of wind turbines may have to be reevaluated if it is determined that they affect the animals' conservation status.

"Our predictions highlight that seals may routinely be exposed to potentially hazardous levels of underwater noise during pile driving, with potential implications for the conservation status of some populations. To reduce these potential impacts, regulators and industry are currently investigating engineering solutions to reduce sound levels at source, and methods to deter animals from damage risk zones in order to potentially reduce auditory damage risk," Hastie added.

Next, the research team plans to use special "seal headphones" to further evaluate UK seals' hearing, as well as monitor individual seals' movements at sea, and collect long-term data on their growth, reproduction and survival.

Harbor seals live around the coasts of the North Atlantic and North Pacific from the subtropics to the Arctic. Around 30 percent of European harbor seals are found in the United Kingdom alone.

A viral epidemic swept through seal populations in the region back in 1988 and again in 2002, decimating their numbers, and the sea mammals are still on their road to recovery. And though wind turbines provide a unique alternative energy source for humans, if they are proven to negatively impact this recovering species, scientists may have to look into engineering solutions to reduce noise levels.

The findings were published in the Journal of Applied Ecology.

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