The Effects of Underwater Noise Pollution and Offshore Wind Farms on Marine Mammals
Underwater or ocean noise can have natural/biological sources or anthropogenic sources, otherwise known as human-made noise. Ocean noise is very important to monitor due to its impact on the environment and the organisms within. Natural sources of ocean noise have physical/geophysical, atmospheric, and geological aspects. These aspects can include wind and precipitation at the ocean surface, storms, seismic activity such as earthquakes, and other natural phenomena. Biological sources include marine mammal sound production as well as sound made by fish and other marine organisms. These sources usually do not harm the species within our oceans; it is anthropogenic sources that impact ocean life negatively, especially marine mammals. Some examples of anthropogenic contributions to ocean noise are vessel traffic, oil/gas industry activities, seismic or sonar profiling, construction, and explosive testing. The combination of all these is known as noise pollution. Since the industrial revolution, noise pollution has increased within our oceans making it hard for marine mammals to escape. This can cause damage to their hearing and their overall bodies (Ocean Noise and Marine Mammals, 2003).
The known effects of anthropogenic noise on marine organisms studied by scientists mainly affect their behavior and health. Marine mammals are the most studied aquatic creature because they have shown side effects to these noises. Mammals, such as whales, rely heavily on hearing to feed, migrate, and mate. When other sounds interfere it can cause confusion. If those sounds have a high enough frequency it can cause internal damage to these creatures. Marine mammals who use echolocation, commonly known in odontocetes, are more sensitive to these noises and show more behavioral changes. Typical changes in behavior are shorter surfacing, shorter dives, fewer blows per surfacing, longer intervals between each blow, changes in growth and reproduction and changes in predator and prey interactions. Movements and migration patterns also change due to the location of the noise, so mammals will purposely swim out of their way to avoid a sound that is hurting them, and even sometimes end up washed ashore to escape the noise. Internally, it causes hearing sensitivity and, for mammals that use echolocation, can alter their abilities to give out and receive signals (Ocean Noise and Marine Mammals, 2003). This then makes it hard for them to understand their surroundings. Stress levels are known to increase in these areas as well. These are all known side effects of ocean noise pollution studied throughout the years. There has been action to decrease the amount within the oceans for the sake of the mammals. These changes include quieter engines, less shipping traffic, less military explosive tests and safer sonar equipment. However, something new could be adding to this noise; offshore wind turbine farms (Williams et al., 2015).
Offshore turbines, or wind farms, are a source of renewable energy. While they are not a new development, more are being made and placed within our oceans to give us alternate energy. The problem is construction generates immense noise and to keep them running could be harmful to marine life, especially marine mammals. To construct these turbines, seismic surveys need to be conducted to understand and map out the seafloor to evaluate where these structures could be properly placed. During these surveys, sound waves are produced and bounce off objects; these waves return back to the source to reveal the image. This is done over the entire sea floor where construction is planned on building these turbines and these sounds can be heard for miles. Pile driving is another method used to build turbines. This is a machine that digs into the soil to provide a strong foundation to support these structures. These machines then drive steel or concrete into the ground. This whole process generates an extreme amount of noise. Once the whole construction process is over, the turbines themselves create noise which can be heard by all marine life miles of the original area. While these machines are being used for alternative energy, their overall construction and use add to the problems of noise pollution (Bailey et al., 2010).
Hopefully in the near future, noise pollution can decrease, making the ocean less abrasive and loud for the marine mammals living within it. If it continues to increase, long term effects may occur and possibly create permanent damage to certain marine species.
Intern at Cape May Whale Watch and Research Center, Stockton University
Bailey, H., Senior, B., Simmons, D., Rusin, J., Picken, G., Thompson, P.M. (2010). Assessing underwater noise levels during pile-driving at an offshore windfarm and its potential effects on marine mammals. Marine Pollution Bulletin. 60(6), 888-897. https://doi.org/10.1016/j.marpolbul.2010.01.003
National Research Council (US) Committee on Potential Impacts of Ambient Noise in the Ocean on Marine Mammals. (2003). Ocean Noise and Marine Mammals. National Academies Press (US).
Williams, R., Wright, A.J., Ashe, E., Blight, L.K., Bruintjes, R., Canessa, R., Clark, C.W., Cullis-suzuki, S., Dakin, D.T., Erbe, C., Hammond, P.S., Merchant, N.D., O’Hara, P.D., Purser, J., Radford, A.N., Simpson, S.D., Thomas, L., Wale, M.A. (2015). Impacts of anthropogenic noise on marine life: Publication patterns, new discoveries, and future direction in research and management. Ocean and Coastal Management. 115, 17-24. http://dx.doi.org/10.1016/j.ocecoaman.2015.05.021