In the open Pacific, underwater noise levels have been doubling in intensity every decade since the 1960s. Why is this a concern? Marine animals use sound the way terrestrial animals use vision – to communicate, to detect predators and prey, and to navigate. Sound travels five times more efficiently in water than it does in air, whereas light, as divers know, does not travel as well in water.
While most people are aware of the hauntingly beautiful calls of resident killer whales and the more frenetic chatter of Pacific white-sided dolphins, smaller marine animals, such as fish and invertebrates, also use sound. For example, plainfin midshipmen use sound to define their breeding territories, and herring produce clicks at night that seem to play a role in maintaining their school. Increasing underwater noise creates acoustic smog that reduces the ability of these and other marine animals to acquire information about their environment.
I have had a long term interest in this issue, and was fortunate enough to be asked to help WWF-Canada organize a workshop called “Finding Management Solutions for Underwater Noise in Canada’s Pacific“ that was held here at the Aquarium in June. We brought together a broad range of people including marine planners, managers, government regulators, ENGOs, noise expert Lindy Weilgart (Dalhousie University) as well as Erich Hoyt, noted expert on Marine Protected Areas, who gave a sold-out public lecture while he was here. Lance Barrett-Lennard, senior marine mammal scientist at the Aquarium, convened the workshop.
The purpose of the workshop was to provide a forum for discussing the management and regulatory methods and approaches for minimizing and mitigating underwater noise, and to develop guidance tools for marine planners and regulators. Lofty goals to be sure, but I think there was a general feeling that real progress was made. Although we didn’t have the expertise in the room to develop absolute noise criteria, we left feeling motivated and with a feeling of hope that there are a number of tools that can be used to mitigate underwater noise.
Vessel traffic, and particularly commercial shipping, is the main contributor of underwater noise in the Pacific (in the Atlantic, seismic surveys for offshore oil and gas also add significant noise). Propeller cavitation is the largest source of noise on most vessels, and merchant ships can vary by up to 40 dB in how much underwater noise they make.
The below sound clip is an example of acoustic masking. Listen to the sounds of the I-15 killer whales calling, only to be drowned out by noise from a cruise ship that comes around the corner. Sound clip courtesy of Orcalab.
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Providing financial incentives such as reduced port fees to motivate ship owners to quieten their vessels is one tool that was repeatedly mentioned at the workshop as a positive solution. The Green Marine certification program, which the Vancouver Aquarium recently joined, is a voluntary initiative that works towards reducing the environmental footprint of marine shipping operations. This program addresses important issues such as invasive species and greenhouse gas emissions, and therefore holds great promise if it can incorporate noise into the list of the major environmental issues it addresses. I am hopeful!
Blog post written by Kathy Heise, research associate, cetacean research lab, Vancouver Aquarium.
 This was actually the 2nd workshop that I have been able to help organize. The first was held early in 2012 and resulted in the summary report Ocean Noise in Canada’s Pacific.