Last week was Ocean Noise Week at NOAA. NOAA and the US Office of National Marine Sanctuaries have listed ocean noise as a national issue -an issue that affects the numerous marine sanctuaries in US waters.
The oceans are naturally noisy places. Natural physical processes such wind and wave action, rain, cracking ice, and undersea earthquakes and eruptions contribute to ambient (background) noise throughout the world’s oceans. Animals that live in the oceans not only have adapted their hearing to these sounds they also take advantage of them, for example for navigation. In turn, marine animals produce a vast array of sounds themselves, from the largest animal -the blue whale, to some of the smallest such as snapping shrimp.
But, marine life relies on sound. Animals use sound to communicate, find prey, and navigate. Sound is much more important that sight or smell in the oceans because it can travel so much further. Marine mammals are particularly reliant on sound. However, noise in the oceans has been steadily increasing with the increase in human activity in and on the world’s oceans. Activities including shipping, military sonars, oil and gas explorations, fishing activities and construction all contribute to ocean noise levels.
Such guidance are necessary as human generated sounds span a wide range of frequencies that often overlap with marine mammal hearing abilities and so have the potential to interfere with an animal’s ability to communicate, detect potential threats such as predators, and find and capture prey. Removing or limiting the impacts of noise on marine life is critical. In extreme cases, marine mammals can suffer permanent hearing damage or even death as a result of exposure to human related sounds. Temporary hearing damage is another risk, as well as changes to an animal’s normal behavior that can result in lower chances of reproduction and/or survival. Through the process of creating the Acoustic Technical Guidance document NMFS produced acoustic thresholds for the onset of permanent threshold shifts (PTS -permanent hearing damage) and temporary threshold shifts (TTS -temporary threshold damage). These thresholds allow government agencies, industry and any one proposing activities that will introduce noise into the oceans to evaluate and understand the potential extent of their impacts and how best they can mitigate the impacts.
Much of our work revolves around understanding the impacts of noise on marine mammals and how we can introduce ways to minimize any impacts. We are currently collecting acoustic data in the inland coastal waters of the Salish Sea to better understand ambient noise levels and how they vary over time. You can check out what this underwater world sounds like yourself through our live-streaming hydrophone. And, in collaboration with our colleagues at the University of St. Andrews we have also developed PCoD -an interim framework for assessing the population consequences of noise disturbance on marine mammals.
To learn more about our work on ocean noise check out some of our projects and recent publications:
Passive Acoustic Monitoring
Population Consequences of Disturbance (PCoD)