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"Right now, the million-dollar question is: Does this disturbance lead to changes in population levels of marine mammals? That's what these long-term studies are ultimately trying to find out," says Nathan Merchant. (Credit: Peter Asprey/Wikimedia Commons)

dolphins

Monitors track noisy ships in dolphin habitat

Too much noise from shipping can stress out marine mammals, so scientists have developed a technique to monitor ship traffic and noise in a protected dolphin habitat in Scotland.

The effort is focused on the Moray Firth, the country’s largest inlet and home to a population of bottlenose dolphins and various types of seals, porpoises, and whales. This protected habitat also houses construction yards that feed Scotland’s ever-expanding offshore wind sector.

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Projected increases in wind farm construction are expected to bring more shipping through the habitat—something scientists think could have a negative impact on resident marine mammals.

“Different ships emit noise at different levels and frequencies, so it’s important to know which types of vessels are crossing the habitats and migration routes of marine mammals,” says Nathan Merchant, a postdoctoral researcher at Syracuse University. “The cumulative effect of many noisy ship passages can raise the physiological stress level of marine mammals and affect foraging behavior.”

Merchant says underwater noise levels have been increasing over recent decades. “These changes in the acoustic environment affect marine mammals because they rely on sound as their primary sensory mode. The disturbance caused by this man-made noise can disrupt crucial activities like hunting for food and communication, affecting the fitness of individual animals.”

He adds: “Right now, the million-dollar question is: Does this disturbance lead to changes in population levels of marine mammals? That’s what these long-term studies are ultimately trying to find out.”

Due to a lack of reliable baseline data, Merchant and his collaborators at the University of Aberdeen have figured out how to monitor underwater noise levels, using ship-tracking data and shore-based time-lapse photography.

These techniques, detailed in a study published in Marine Pollution Bulletin, form a ship-noise assessment toolkit, which Merchant says may be used to study noise from shipping in other habitats.

Source: Syracuse University

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