SEQUIM, Wash. The rise of ocean infrastructure development to tap energy sources such as tides, offshore wind and natural gas will require more pile driving, the practice of pounding long, hollow steel pipes called piles into the ocean floor to support energy turbines and other structures. But pile driving creates loud, underwater booms that can harm fish and other marine animals.
Many scientists and regulators have assumed that limiting the combined amount of sound created during the course of a pile driving project can minimize harm to animals. But new research published in PLoS ONE indicates that if an individual blow to a pile rises above a particular sound level, fish can be irreparably harmed. The finding has led scientists to recommend the first-ever sound threshold for pile driving that is based on actual fish responses instead of estimates. It's hoped that regulators will use the threshold to help evaluate pile driving project applications.
"Our results can help regulators permit ocean development while also protecting marine life," said bioacoustician Michele Halvorsen, who led the research for Battelle, which manages the Department of Energy's Pacific Northwest National Laboratory. "This is the first research that used controlled laboratory tests to reliably measure the affects of pile driving on fish."
Halvorsen conducts research at PNNL's Marine Sciences Laboratory in Sequim, Wash.
Hitting a steel pile with a large hammer produces sound that causes water pressure changes that impact fish. Sudden changes in water pressure can cause gases such as oxygen to come out of fish blood faster than normal, leading to a decompression sickness much like the bends that divers experience when they rise to the surface too fast. Pressure changes also affect a fish's swim bladder, an internal, air-filled sac that helps the fish maintain weightlessness at different water depths. Alternating pressure changes cause the sw
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DOE/Pacific Northwest National Laboratory