Oceans silenced by Covid reveal effect of human activity on marine life

Study could also lead to the world's first complete map of the oceans

The listening posts system works in the same way as a whale searching for food. Getty Images
The listening posts system works in the same way as a whale searching for food. Getty Images

The relative silence caused by the coronavirus pandemic is being used by researchers to build a listening network that could eventually create the first map of the world's oceans.

On Thursday, marine biologists unveiled a listening network to help map the oceans and study how human behaviour and noise affect marine life.

As the pandemic gripped the world’s land masses, human noise in the oceans was largely silenced, with shipping, exploration and leisure operations curtailed or stopped.

Scientists have linked listening posts, called hydrophones, around the globe so that they can pick up sounds from thousands of kilometres away, allowing researchers to map the oceans and better understand marine life.

This map from the IQOE-endorsed JOMOPANS project shows the difference between the total noise level and the natural noise level with differences up to 30 decibels (dB). The underwater noise was measured at 15 locations across the North Sea for a year. Shipping noise dominates human additions of noise in the North Sea. While 30 dB on its own is not loud, the superimposition raises the level significantly higher than natural noise. JOMOPANS
A noise map of the North Sea in Europe JOMOPANS

The system works in the same way a whale searches for food or a warship can detect a submarine – but on a much larger scale.

Dr Ed Urban, project manager at the International Quiet Ocean Experiment's Scientific Committee on Oceanic Research, said co-operation will be key during the research.

“[Hydrophone] operators should see benefits of co-operation, including the ability to map larger areas of the ocean and finally the entire global ocean. No one has attempted such a network previously,” Dr Urban told The National.

“The ocean science community is at the beginning of encouraging an international ocean listening network, which could be part of the Global Ocean Observing System,” he said.

“Success depends on the continuing willingness of individual hydrophone operators to contribute their data to a permanent archive.”

The team identified 231 non-military hydrophones – the largest concentration is in North America – and hopes to eventually have 500 of them in the listening network.

The hydrophones will capture the signals of whales and other marine life while also assessing levels of human activity.

Combined with other sea-life monitoring tools, such as animal tagging, the work will help to reveal the extent to which noise affects ocean species.

Sound travels far in the ocean and a hydrophone can pick up low-frequency signals from hundreds, even thousands, of kilometres away.

"Measuring variability and change in ambient, or background, ocean sound over time forms the basis for characterising marine 'soundscapes'," said project collaborator Peter Tyack, a professor of marine mammal biology at the University of St Andrews, Scotland.

"Assessing the risks of underwater sound for marine life requires understanding what sound levels cause harmful effects and where in the ocean vulnerable animals may be exposed to sound exceeding these levels.”

The team is working to create a global data repository with contributors using standardised methods and tools to measure and document ocean soundscapes and their effects on animals.

Updated: April 8, 2021 06:50 PM

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