As oceanographic noise pollution rises, there is a growing concern for the stress it places on marine life, as well as for rising trends in the amount of noise pollution caused by industry and anthropogenic, or human-caused, sound. Because of the nature of sound in the ocean, noise pollution and, more broadly, the soundscape in the ocean are difficult to research. A seemingly insignificant problem to humans causes significant changes in marine life, and in order to explore the link between population changes and noise pollution, the complex causes of anthropogenic sound in ocean soundscapes must be explored.
Why is noise pollution in the oceans that important? At least in my eyes, even though humans avoid dealing with the firsthand effects of noise pollution in oceans, the broader consequences on the larger oceanic ecosystem harms us more than we think. As the delicate balance in the ocean changes due to behavioral and physiological changes on certain marine life, entire populations of marine life shift and shrink, causing immeasurable harm to other species of marine animals, and creating a never ending domino effect, changing the marine environment forever.
To first understand how underwater sound is changing, ambient noise and the bioacoustics of the ocean, that is the production, usage, and reception of sound in the ocean by animals, have to be considered. Humans have long known that underwater creatures utilize and communicate using noise, shown from the myths of singing sirens and dolphins rescuing Arion, a Greek musician from the sea, but in more recent times, much work has been done to identify and qualify the marine acoustic environment (Stocker 2002, 16). Most of the noise previously thought of as “background” noise in oceans has been now recognized as being crucial sounds for animal survival and is being used by sea creatures to communicate, navigate, hunt, bond and breed. Most people consider the ocean to be a silent place because humans are poorly adapted for underwater sound, in juxtaposition to say air, which even produces the sound of our voice.
The ocean’s acoustic environment includes many sources of sound, mostly naturally occurring noises from wind, waves, tides, and currents, but anthropogenic sound has, in fact, been present since the days of the first seafaring people (Stocker 2002, 16). Over the past 100 years though, anthropogenic sound underwater has exponentially increased, adding to the ambient noise, and drowning out sources of ambient noise already present. Of those sources that were drowned out, perhaps the most important is naturally occurring, biological ambient noise.
Some of the most recognizable naturally occurring, biological sounds include the songs of whales and dolphins. In addition to those, there are countless other sources of biological noise, including scraping, grinding, grunting, and singing produced by fish, crustaceans, mollusks and cnidaria.
Katherine Payne, an acoustic biologist, along with her husband Roger Payne, in the 1970s made an album of humpback whale songs, which became one of the best selling natural sounds album of all time (May 2014).
Whales’, and other animals’, use of sound can be categorized in two different ways, active usage, or when an animal creates a sound to interact with other animals and their environment, or passive usage, when an animal responds to environmental and ambient sounds it does not create. Usage of sound becomes an extremely important evolutionary tool that sea animals rely on in order to detect and locate prey and predators, detect proximity to co-species and changing environmental conditions, and to navigate (Stocker 2002, 23). But as these sounds become harder to discern or more difficult to create effectively, their significance diminishes.
In order to explore the specific evolutionary changes in marine mammals, and even more generally marine life caused by noise pollution in ocean soundscapes, the specific sources of oceanographic noise pollution have to be thoroughly explored to gain a deeper understand of the true magnitude of anthropogenic noise. McCarthy, in International regulation of underwater sound, thoroughly describes the complexities of various industries that contribute the most, including shipping, dredging, coastal constriction, offshore oil and mineral exploration, boating, fishing, and military activities. McCarthy examines and presents the increasing trends of noise pollution in those industries are provides a useful basis of explaining the worsening conditions of underwater noise pollution.
Sources of historical data of ambient noise from each of these industries can be found by utilizing data intended for military research projects such as the US Navy’s Sound Ocean Surveillance System (SONUS) which utilized networks of hydrophones to listen for and record signals from enemy submarines. Since such projects were clearly intended for military applications, it sometimes lacks the focus that is required to provide detailed data, but connected to other data, such as the increase in the amount of ships on the ocean or the number of offshore oil rigs.
The recording technology utilized by such projects however remains applicable in monitoring and recording underwater noise. Hydrophones, analogous to microphones above water, convert sound in water into electrical signals that can be played back. Demonstrating the usage and sound produced by this type of recording tool, I’ve made a recording of the Brodie Aquatics Center.
Made by placing the hydrophone into the edge of the pool, I recorded the pool in which kayakers were practicing. This created noise analogous to what animals in the distance would create. Since the water was relatively calm while recording, there is not as much variation in sound as there would be in the ocean, but the recording does present an accurate enough representation of how sound would be monitored in oceans to collect data on ambient noise in the ocean.
Specific cases of deleterious effects on marine mammals caused by humans include abandonment of entire habitats by significant populations of Gray and killer whales due to icebreaking, some even 50 kilometers away, and sonar caused noise pollution causing mass stranding of beaked whales (National Research Council 2005, 14). The National Research Council Committee notes that some of these small changes in behavior for these mammals over time lead to more significant effects.
“Although there are many documented, clearly discernible responses of marine mammals to anthropogenic sound, responses are typically subtle, consisting of shorter surfacings, shorter dives, fewer blows per surfacing, longer intervals between blows, ceasing or increasing vocalizations, shortening or lengthening vocalizations, and changing frequency or intensity of vocalizations. Some of those changes become statistically significant for a given exposure, such as increases in descent rate and increases or decreases in ascent rate of northern elephant seals.” (National Research Council 2005, 14)
But the council also notes that “it remains unknown when and how these changes translate into biologically significant effects—effects that have repercussions for the animal beyond the time of disturbance, effects on the animal’s ability to engage in essential activities, and effects that have potential consequences at the population level” (National Research Council 2005, 13).
The only reasonable way of curbing the amount of anthropogenic noise introduced in oceanographic soundscapes is introducing legislature and through focusing on policy and governmental decisions regarding the protection of ocean soundscapes. Most research regarding noise pollution in oceans contain an abundance of raw data, hinting at the negative consequences caused by noise at certain frequencies, but barely touching on the actual evolutionary changes caused by humankind inadvertently on marine life.
A small amount of research on the most alarming consequence, in my mind, of underwater noise pollution is problematic. Stronger data collection efforts using more focused networks of hydrophones and creating more concrete links with ambient noise levels might usher in new support towards minimizing the destruction of underwater soundscapes.
The relevance of underwater noise pollution to humankind is that the interconnectedness of humans and animals is placed into danger if humans carelessly or recklessly endanger the other. Placing the important of marine life as a food source aside, shifts in populations of marine life alter our enjoyment and our enchantment of the seas forever.
International Conference on the Effects of Noise on Aquatic Life. 2012. The effects of noise on aquatic life ed. Arthur N. Popper. New York: Springer.
Jasny, Michael. 2005. Sounding the depths II the rising toll of sonar, shipping and industrial ocean noise on marine life. New York, NY: Natural Resources Defense Council.
Low-frequency sound and marine mammals: Current knowledge and research needs1994. , eds. Committee on Low-Frequency Sound and Marine Mammals, Ocean Studies Board, Commission on Geosciences, Environment, and Resources, National Research Council., National Research Council (U.S.). Committee on Low-Frequency Sound and Marine Mammals. Washington, D.C.: National Academy Press.
May, Michael. “Recordings That Made Waves: The Songs That Saved The Whales : NPR.” NPR.org. Last modified December 26, 2014. http://www.npr.org/2014/12/26/373303726/recordings-that-made-waves-the-songs-that-saved-the-whales.
McCarthy, Elena. 2004. International regulation of underwater sound: Establishing rules and standards to address ocean noise pollution. Boston: Kluwer Academic Publishers.
National Research Council (US) Committee on Characterizing Biologically Significant Marine, Mammal Behavior. 2005. Marine mammal populations and ocean noise: Determining when noise causes biologically significant effects, ed. National Academies Press (U.S.). Washington, D.C.: National Academies Press.
Stocker, Michael. “Ocean Bio-Acoustics and Noise Pollution.” Soundscape: The Journal of Acoustic Ecology 3, no. 2 (Winter 2002): 16-28.