A new study conducted by the University of St. Andrews in Scotland reveals that noise coming from offshore wind turbine construction affects the sensitive hearing of seals.

Dr. Gordon Hastie of St. Andrews's Sea Mammal Research Unit led a team of researchers in investigating the impact of offshore wind turbines on the hearing of marine mammals. Their goal was to develop possible solutions for reducing noise levels through engineering.

In 2012, while the wind turbines were being installed, the researchers attached GPS data tags on 24 harbor seals in order to monitor the effects of pile driving noise on the animals.

By combining data collected from the GPS loggers, acoustic propagation models and the pile driving, Hastie and his colleagues discovered potential damage to the seals' auditory faculty. The models used by the researchers revealed that the marine mammals were subjected to high levels of noise — enough to damage their hearing thresholds.

While they were able to obtain data to prove the effects of noise on the hearing of the harbor seals, the researchers noted that they do not have data on how the pulsed sound of pile driving impacts animals. Previous studies, however, suggest that such high levels of noise can damage the hearing of humans and other terrestrial creatures.

"These are some of the most powerful man-made sounds produced underwater, noise capable of travelling large distances underwater," Hastie said. He explained that the noise could have significant effects on the conservation status of harbor seal 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," he said. 

Hastie added that harbor seals, like most other marine mammals, have very sensitive hearing capable of detecting much higher frequencies than that of human hearing.

He believes the seals use this acute hearing when they mate or when they try to avoid potential predators. The ability might also help them to navigate through the depth of the ocean and to find food.

The researchers said the findings of their study are important in ensuring the safety of the harbor seals. Since the marine animals are protected under European law, their conditions should be taken into account before constructing wind farms.

This study was published in the Journal of Applied Ecology.

Photo: U.S. Fish and Wildlife Service Northeast Region | Flickr