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As the world looks for renewable, fossil fuel-free ways to power an increasingly warmer and crowded planet, two technologies are becoming more popular: wave power and tidal power. Both use the natural motion of the sea to generate energy, and by 2020 coastal power is expected to become a US $10 billion industry.
By using massive turbines to tap into the rise and fall of waves or the surging tide, coastal power can provide a carbon-free flow of energy. But just because a new technology solves one problem doesn’t mean it won’t cause others, and researchers studying coastal power are worried about one issue in particular: noise.
Any machine with moving parts makes noise. And in the dark depths of the sea, animals depend on sound for everything from communication to navigation. In the ocean, light doesn’t penetrate very far, while sound travels even farther than it does through air, so sound is particularly important to marine life. Might the whirring and pounding of wave and tidal turbines be like a jackhammer in the deep?
Granted, the sea is far from silent: it contains a symphony of natural sounds, from whale song to the clacking of snapping shrimp. But human inventions—from ships to seismic surveyors to offshore rigs—to, potentially, wave and tidal turbines—threaten to drown all this out.
Scientists still aren’t sure of coastal power’s noise pollution potential, but marine biologist Matt Pine is trying to find out.
Pine recently led a study to examine how noise pollution might affect the life in Kaipara Harbor, in northern New Zealand, where tidal power generators are being considered for installation (though that project is currently stalled for economic and political reasons).
Pine and his team are concerned about a number of species, especially crustaceans. As larvae, most crustaceans, such as lobsters, spend their days drifting on ocean currents. Once they approach the juvenile stage, they metamorphose, losing their ability to eat, but gaining the ability to swim. From there, it’s a life or death race to reach the shore where they can complete the transition to adulthood. But to find the shore, they need to hear cues from the shoreline. If noise pollution interferes, that could imperil these species, many of which hold crucial spots near the base of the food chain.
“It’s a race against time because they can’t eat anything, and the longer they spend in the swimming phase the less energy they have,” says Pine. “They listen for the sound of the coast, and they swim for that sound,” he says. “When you put a tidal turbine in an estuary, you could potentially mask these natural sounds.”
Since the Kaipara Harbor tidal generators have yet to be built, Pine’s research can only provide the “before picture” in advance of any potential effects from noise pollution.
As it stands, research on wave and tidal power noise is scant, partly because the technology is relatively new, but also because not many people are expecting it to present much of a problem, says Jakob Tougaard, a marine biologist.
On the other side of the world, in the Danish North Sea, Tougaard and his colleagues are testing the potential threat of wave turbine noise. Rather than surveying the coastal soundscape, Tougaard studied the intensity of noise created by a prototype wave power generator called the Wave Star energy converter. The machine uses huge floating cylinders on metallic arms to catch the momentum of incoming waves.
Tougaard found that the noise produced by the converter is “very weak,” too quiet to disrupt the communications of local sea creatures (though, his study focused on marine mammals). “There are good reasons for concern for marine mammals with underwater noise,” says Tougaard. But “if we’re talking about seals and dolphins and whales, they are likely unable to hear [the generators] unless they are at very close range.”
Whether tidal power will become part of the noise pollution problem is an open question. From Tougaard’s research the answer seems to be “probably not,” or at least, “not more than anything else,” at least in relation to marine mammals. But as Pine’s research shows, the threat of unintended consequences looms large—though not nearly as large as the threat of unmitigated climate change.