Have you ever wondered how we depicted the seabed or locate oil or natural gas under the ocean? While seismic airgun is definitely one of the ways.
Seismic survey is a process that used seismic airgun blasting to explore oil and natural gases and it also does geophysical surveys of the seafloor (Ocean care, n.d.). The seismic airgun released sound wave from the blasting and the reflected soundwave will be recorded after hitting the seafloor. However, the use of seismic airgun has caused significant noise pollution in the ocean. Unlike light pollution, noise is capable of penetrating to a deeper part of the ocean and spreading at a faster rate. The noise emitted by the airgun blasting is able to transfer hundreds or even thousands of meters into the water column. Seismic airgun has been considered as the most severe cause of ocean noise pollution by humans.
Additionally, it is extremely difficult to estimate the exact affected area as the surveying process is constantly moving. The seismic airgun releases a blasting shot in a tight sequence that operates 24 hours and this can last for weeks or even months (Ocean care, n.d.). According to Robbins (2019), each blasting from the airgun is proximately up to 260 underwater decibels (200 decibels in the atmosphere) which are higher than container ships as they only create noise up to 190 decibels (130 decibels in the atmosphere). According to DOSITS (2019), the effect of the sound wave might be longer than expected because the sound wave are frequently reflected among the seafloor and rocks.
Source: https://www.youtube.com/watch?v=5P_LH7EG6nU&t
The seismic survey process has affected various species such as the zooplankton, fish, whales or even giant squids from the deeper ocean. In the study by Mccauley et al. (2017), they argued the seismic airgun has caused the declining of zooplankton. As the basis of the food chain, the reduction of zooplankton will have a major effect on the marine ecosystem. Furthermore, the intense broadband pulses by the seismic airgun have affected the behaviours of dolphins and whales (Weilgart, 2013).
Dolphins and whales might suffer from loss of hearing, acoustic stress or even internal organ injuries. The intense pulses also masked their biosonar which might further affect their communication or navigation ability hence, leading to mass stranding event. Observations revealed that whales and dolphins often avoid the areas near seismic airgun. From this, we see how some marine species are being forced to alter their behaviour to protect themselves from the harmful seismic airgun.
Several countries have begun to reduce and control the use of seismic airgun. However, the United States has allowed the petroleum companies to use seismic airgun for oil and gas exploration in the Atlanta ocean recently (Robbins, 2019). This might simply worsen the condition under the ocean. The endangered North Atlantic right whale is highly affected by this new regulation and its population have continued to decline. Therefore, NGOs are still actively protesting against the government and corporations to decrease or even ban the use of seismic airgun to prevent further disaster.
Source: https://www.youtube.com/watch?v=9CsHz3lesC4
Cheers,
Shee Wen & Nicole 
References
DOSITS. (2019, April 23). Seismic Airguns. Retrieved October 17, 2020, from https://dosits.org/animals/effects-of-sound/anthropogenic-sources/seismic-airguns/
McCauley, R.D., Day, R.D., Swadling, K.M., Fitzgibbon, Q.P., Watson, R.A. & Semmens, J.M. (2017), “Widely used marine seismic survey air gun operations negatively impact zooplankton”, Nature ecology & evolution, vol. 1, no. 7, pp. 195-195.
Ocean care. (n.d.). Silent Oceans: Causes of underwater noise. Retrieved October 17, 2020, from https://www.oceancare.org/en/our-work/ocean-conservation/underwater-noise/silent-oceans-causes-underwater-noise/
Robbins, J. (2019). Oceans Are Getting Louder, Posing Potential Threats to Marine Life. Retrieved October 17, 2020, from https://www.nytimes.com/2019/01/22/science/oceans-whales-noise-offshore-drilling.html
Weilgart, L. (2013). “A review of the impacts of seismic airgun surveys on marine life.” Submitted to the CBD Expert Workshop on Underwater Noise and its Impacts on Marine and Coastal Biodiversity, 25-27 February 2014,
London, UK. Available at: http://www.cbd.int/doc/?meeting=MCBEM-2014-01