Contrary to the popular belief that our oceans are actually “Silent”, many marine organisms actually rely on their sense of hearing for essential life functions (Jones, 2019). Various marine mammals, fish and other organisms use sound as a primary method of communication, to locate mates and prey, as well as in the navigation and orientation of their environment (Simmonds & MacLennan, 2005). Even abiotic sound sources— sounds generated by the environment, such as by the crashing of waves or the sound of currents going over reefs, similarly remain important for marine organisms in orientating their environments (Peng et al., 2015; Popper et al., 2003). 

However increasing anthropogenic noise emissions, driven by the continued increase in the utilisation of our oceans and seas, have led to growing negative impacts on marine organisms (Peng et al., 2015). Figure 1 highlights a range of underwater anthropogenic sound sources. 

Figure 1: Undersea Sound Sources (Jones, 2019).

One significant source of anthropogenic underwater noise pollution is the shipping industry. In their review of the literature regarding the effects of ship noise on marine life, Erbe et al (2019) have described noise produced by ship traffic to be the “most ubiquitous and pervasive” source of anthropogenic noise in our oceans, responsible for the production of low-frequency noise that has been growing at an average rate of 3dB/decade (p.2). 

Ships mainly emit noise as a by-product when bubbles produced during the rotation of their propellers (a process known as cavitation) break underwater. Noise is also emitted from the vibration of the ship’s engine, and from the movement of the ship’s hull through the water (Clean Arctic Alliance, 2023; EMSA, n.d.). The level of noise pollution significantly increases with the size of the vessel. According to Hildebrand’s (2009) study of anthropogenic noise in the ocean, a small engine boat operating at 20 knots produces a much lower sound level of 60dB, when compared to a 173m cargo vessel operating at 16 knots, which produces 192dB, when measured at 1m away. Figure 2 below depicts the geographical distribution of global shipping noise emissions in 2019, created via a global modelling of noise source energy emissions measured from ships (63Hz). As seen in the Figure, the main shipping lanes (e.g. Straits of Malacca, Suez Canal, South China Sea and the English Channel), see the highest noise contributions from shipping. Figure 3 below highlights how noise energy emissions have generally been increasing along the world’s main shipping lanes. 

Figure 2: Global map of underwater noise emissions from ships in 2019, at 63Hz (Jalkanen et al., 2022).

Figure 3: Changes in underwater noise source energy emissions, 2014–2019, at 63Hz (Jalkanen et al., 2022).

Such noise pollution emitted by the shipping industry along shipping lanes has negatively impacted the marine biodiversity surrounding it, often altering their behaviours. One of the first pieces of evidence was presented by Rolland et al. (2012), who have shown how reduced ship traffic after the 11 September 2001 attacks, has led to a subsequent 6dB decrease in underwater noise, especially that below the range of 150Hz. This noise reduction was then associated with decreased stress levels in endangered right whales, as evidenced by lower levels of stress-related faecal hormone metabolites. This is evidence to show that increased exposure to low-frequency noise emissions from ships may be associated with chronic stress in whales. In other studies, dolphins were found to alter the frequency of their whistles in response to greater ship noise (Morisaka et al., 2005), while  humpback whales have been found to alter their foraging behaviour, with increasing ship noise associated with slower descent rates (Blair et al., 2016). Lastly, a study by Simpson et al (2016) has found the presence of underwater anthropogenic noise to increase fish mortality by predation. 

Having gained an understanding of the harmful impacts that noise pollution from the shipping industry has on marine life, in a subsequent blog, we will examine the various solutions proposed for this problem. 

 

References 

Blair, H. B., Merchant, N. D., Friedlaender, A. S., Wiley, D. N., & Parks, S. E. (2016). Evidence for ship noise impacts on humpback whale foraging behaviour. Biology Letters, 12(8), 20160005. https://doi.org/10.1098/rsbl.2016.0005

Clean Arctic Alliance. (2023, February 1). NGOs call on UN shipping body to reduce underwater noise impact on marine life. Eco-Business. https://www.eco-business.com/press-releases/ngos-call-on-un-shipping-body-to-reduce-underwater-noise-impact-on-marine-life/#:~:text=An%20important%20source%20of%20continuous,impact%20on%20the%20Arctic%20ecosystem

Erbe, C., Marley, S. A., Schoeman, R. P., Smith, J. N., Trigg, L. E., & Embling, C. B. (2019). The effects of ship noise on marine mammals—A review. Frontiers in Marine Science, 6, 606. https://doi.org/10.3389/fmars.2019.00606

European Maritime Safety Agency. (n.d.). Underwater noise. https://www.emsa.europa.eu/protecting-the-marine-environment/underwater-noise.html#:~:text=Ships%20are%20reported%20to%20be,the%20hull%20through%20the%20water

Hildebrand, J. (2009). Anthropogenic and natural sources of ambient noise in the ocean. Marine Ecology Progress Series, 395, 5–20. https://doi.org/10.3354/meps08353

Jalkanen, J.-P., Johansson, L., Andersson, M. H., Majamäki, E., & Sigray, P. (2022). Underwater noise emissions from ships during 2014–2020. Environmental Pollution, 311, 119766. https://doi.org/10.1016/j.envpol.2022.119766

Jones, N. (2019, April 10). Ocean uproar: Saving marine life from a barrage of noise. Nature. https://www.nature.com/articles/d41586-019-01098-6

Morisaka, T., Shinohara, M., Nakahara, F., & Akamatsu, T. (2005). Effects of ambient noise on the whistles of indo-pacific bottlenose dolphin populations. Journal of Mammalogy, 86(3), 541–546. https://doi.org/10.1644/1545-1542(2005)86[541:EOANOT]2.0.CO;2

Peng, C., Zhao, X., & Liu, G. (2015). Noise in the sea and its impacts on marine organisms. International Journal of Environmental Research and Public Health, 12(10), 12304–12323. https://doi.org/10.3390/ijerph121012304

Popper, A., Fay, R., Platt, C., & Sand, O. (2003). Sound detection mechanisms and capabilties of Teleost fishes. In S. P. Collin, & N. J. Marshall (Eds.), In sensory processing in aquatic environments (pp. 3-38). Springer. 

Rolland, R. M., Parks, S. E., Hunt, K. E., Castellote, M., Corkeron, P. J., Nowacek, D. P., Wasser, S. K., & Kraus, S. D. (2012). Evidence that ship noise increases stress in right whales. Proceedings of the Royal Society B: Biological Sciences, 279(1737), 2363–2368. https://doi.org/10.1098/rspb.2011.2429

Simmonds, E. J., MacLennan, D. N., & MacLennan, D. N. (2005). Fisheries acoustics: Theory and practice (2nd ed). Blackwell Science.

Simpson, S. D., Radford, A. N., Nedelec, S. L., Ferrari, M. C. O., Chivers, D. P., McCormick, M. I., & Meekan, M. G. (2016). Anthropogenic noise increases fish mortality by predation. Nature Communications, 7(1), 10544. https://doi.org/10.1038/ncomms10544