Research shows that a surge of sea sounds stresses out whales

WWF

When people think about environmental damage in the ocean, massive oil spills like the Exxon Valdez and the offshore oil disaster like the BP blowout two years ago in the Gulf of Mexico come to mind.  The impacts from noise are much more under the radar (ha!). But noisy ocean activities are escalating.

Two Humpback whale (Megaptera novaeangliae) near a small boat, Canada. © J. D. Taylor / WWF-Canada


Look at these figures: a study in southern California showed that deep ocean ambient noise levels in 2003-2004 were 10 to 12 decibels higher than in 1964-1966, an average increase of three decibels per decade. The steep climb in ocean noise is matched by the sharp increase in global shipping. The International Maritime Organization (IMO)  calculates that world seaborne trade figures reached 8.2 billion tons of goods in 2008. If that growth trend continues, by 2060 the 8 billion tonnes of cargo will have grown to 23 billion tonnes.
At WWF, we’re sounding the alarm about this issue: the projected increase in shipping traffic on B.C.’s North Coast will involve hundreds of additional large ships crossing narrow waters, with a corresponding dramatic increase in underwater noise. WWF-Canada’s exploratory ocean noise workshop brought many leading researchers together to share notes on this concern.
Even low levels of noise can harm whales: An eerie after effect of the 9-11 terrorist attacks was confirmation that exposure to low-frequency ship noise is associated with chronic stress in whales.  Researchers at sea taking samples from whales noted how silent the oceans became when ship traffic was halted immediately after the terrorist attacks. They analyzed underwater noise levels before and after the attacks, and compared those data with levels of stress-related hormone metabolites in the fecal samples of right whales that were collected directly before and right after the attacks.  They found a clear correlation: the decrease in background underwater noise corresponded with a decrease in stress hormone levels in the whales. Their findings were published in a peer reviewed study this year:  Evidence that ship noise increases stress in right whales.
Lead researcher, Douglas Nowacek of Duke University, said: “There was a six-decibel decrease in underwater noise in the bay following 9/11, with an especially significant reduction in the low-frequency ranges below 150 hertz. In subsequent years, ship traffic – and noise – were higher, along with the whale’s stress-hormone levels.”
There are solutions: designing quieter ships, restricting or rerouting ship traffic near sensitive habitat, creating marine protected areas for quiet ocean places, and setting noise budgets for certain habitat. Another solution is to develop comprehensive action plans and laws to protect whales and other marine mammals from a variety of threats, including noise. That’s the topic of my next blog.
Stay tuned!