April 28, 2020 — In cities, human lockdowns during the coronavirus pandemic have offered some respite to the natural world, with clear skies and the return of wildlife to waterways. Now evidence of a drop in underwater noise pollution has led experts to predict the crisis may also be good news for whales and other sea mammals.
Researchers examining real-time underwater sound signals from seabed observatories run by Ocean Networks Canada near the port of Vancouver found a significant drop in low-frequency sound associated with ships.
David Barclay, assistant professor of oceanography at Dalhousie University, the lead author of a paper reviewing the phenomena, examined sound power – a way of measuring “loudness” – in the 100 Hz range from two sites, one inland and one farther offshore. He found a significant drop in noise from both.
Generally, we know underwater noise at this frequency has effects on marine mammals,” Barclay said.
“There has been a consistent drop in noise since 1 January, which has amounted to a change of four or five decibels in the period up to 1 April,” he said. Economic data from the port showed a drop of around 20% in exports and imports over the same period, he said.
The deep ocean site, around 60km from the shipping lanes and in 3,000 metres of water, also showed a drop in average weekly noise of 1.5 decibels, or around a 15% decrease in power, Barclay said. “This gives us an idea of the scale over which this reduction in noise can be observed.”
The reduction in ship traffic in the ocean, which Barclay compares to a “giant human experiment”, has had scientists racing to find out the effect on marine life.