For a moment last spring, things got very quiet in the oceans.

The drop in human activity that came with the pandemic resulted in drastic and voluntary sound reductions that ran the underwater gamut: from a drop in shipping noise, the predominant source of man-made ocean noise pollution, to decreases in recreation and tourism. All of it suddenly ceased.

In Alaska’s Glacier Bay National Park, the foraging grounds of humpback whales, the loudest underwater sounds last May were less than half as loud as those in May 2018, according to a Cornell University analysis. A May 2020 paper in the Journal of the Acoustical Society of America found that underwater noise off the Vancouver coast was half as loud in April as the loudest sounds recorded in the months preceding the shipping traffic slowdown.

Chronic underwater ocean noise had been rising over the past few decades, to the detriment of marine life that have evolved to use sound to navigate their world. “There is clear evidence that noise compromises hearing ability and induces physiological and behavioral changes in marine animals,” reads an assessment of marine noise pollution research published in the journal Science in February.

The majority of ocean noise pollution is a byproduct of economic activity. But compared with massively complex issues like climate change, noise is relatively easy to turn down, at least a little. Silencing it at its source has an immediate positive impact: Famously, researchers studying right whales on the East Coast measured a drop in the animals’ stress hormones in the wake of the 9/11 attacks, after shipping traffic abruptly dropped. Even tiny fish larvae are better able to locate the coral reefs where they were born, which themselves emit sound, when the oceans get quiet.

Man-made ocean noise has since ramped back up and is now stabilized near pre-pandemic levels. But it fell silent for long enough last March, April, and May that a global team of scientists is actively scrubbing through audio recordings gathered by around 230 non-military hydrophones — underwater microphones — that monitor ocean noise around the world. They aim to study the “year of the quiet ocean” in the context of ocean sounds before, during, and after the pandemic.

–Excerpted from Vox

Categories: Noise Pollution