At Dalhousie University, Lindy Weilgart has been studying underwater noise for 25 years. Given all the stressors on the ocean, from pollution to absorbing most of the carbon dioxide we’re putting in the atmosphere, we no longer have the luxury of not being precautionary, she says.
Temperatures are rising and water is acidifying as a result. When noise is thrown into the mix, whether it’s from shipping, military sonar or seismic testing, the effects can multiply, and “be greater than the sum of the parts,” so it’s little wonder species’ composition is changing, Weilgart says.
“Yes, you can always make an argument that there’s a natural mortality rate among plankton. They aren’t exactly elephants, so their death rate is fairly high. But (this decline) is definitely a concern,” she says.
“We do this all the time. We underestimate the impact we’re causing and, particularly, we take each impact separately, and we don’t consider that there is a limit. You can’t keep throwing things at nature and not expect there will be some repercussions and nasty surprises.”
Last year, Weilgart produced a report that reviewed 115 primary studies on human-produced underwater noise sources affecting 66 species of fish, 40 species of marine mammals and 36 species of invertebrates. It showed zooplankton suffer high mortality in the presence of noise.
“You’ve got 140 species that are affected by noise. This has to qualify as an ecosystem-wide impact. It’s not going to affect all species in the same way, but most stressors do not.”
She says she used to think plankton weren’t affected by sound.
“I would not have put plankton in one of the categories that I’d initially have been worried about, but here we are. Plankton supports all life in the ocean. That’s why (what’s happening) is particularly worrisome.”
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