On whales and anthropogenic sound pollution

On whales and anthropogenic sound pollution

Whales are the biggest creatures to ever live on this planet. They range in size from 6 feet, 400 pounds to 98 feet, 170 tons (Guasso, R., et. al., 2017). Scientific evidence is mounting that says that anthropogenic sound pollution is detrimental to marine life (Pirotta, et. al. 2018). Studies suggest that such anthropogenic sound pollutants result in mass whale strandings, as well as negatively affect cetaceans’ ability to communicate, navigate, and hunt (Ali, Mustapha,  Balbir, Nafiseh, 2018). There are 4 major types of anthropogenic sound pollution effects on cetacean populations on planet earth: oil rig and global shipping noise, radar, and seismic air guns. 

Whales are wonders of marine life. Many are highly sociable. Female sperm whales are extremely social cetaceans, and they face an interesting dilemma in which their prey of choice, things like giant squid, reside deep in the ocean. Sperm whales’ chosen prey live so deep in the ocean that a juvenile cannot withstand the force of pressure, and so they must be left up near the surface while the mother hunts. Sperm whales have a novel solution to this; they run a rotating daycare, where some mothers stay back while others hunt, then they switch. If attacked, they will group up, juveniles toward the center and adults toward the outside of a circle. They circle up either heads or tails outward, depending on the type of predator present. Adults have even been witnessed risking their own well-being in strategic moves to protect the rest of the group(Whitehead, H. 2018). Once the mothers are done hunting, they use echolocation to find the group again and the daycare cycle continues. This is one of many interesting displays of social behavior witnessed in cetacean species. 

Fin, and Blue Whales have been recorded swimming in arrays near the seafloor. Scientists from the University of California San Diego recorded groups of these whales swimming several kilometers apart from one another, coordinating respiration times (McDonald et. al., 1995). This impressive display of social behavior seems likely, because the scientists recorded the whales and heard alternating calls between the members of each group. Our noise may be destroying this beautiful and important ability.  Many anthropogenic noises can carry for kilometers, up to 4,000km in the case of seismic airguns and 10km for the average shipping vessel(Parsons, 2017). This may drown out vocalizations and render these species unable to communicate (Hatch, L., et. al, 2012). This would be a serious blow, as sound is absolutely vital for whale existence. 

Auditory senses are the most important for a whale in terms of hunting and breeding success, navigation of the sea, and avoiding predators. A humpback whale’s eyesight only works for about thirty feet in clear water(Jebelli, Mustapha, Balbir, Nafiseh, 2018). Olfaction is absent in toothed whales, and present in fetal development but dramatically reduced in adulthood in baleen whales (Kishida, t., et al. 2015).

. With these two options reduced, that leaves the auditory option as the last long-distance option for hunting, communication, and obstacle navigation. Massive organs for creating and receiving sound are what makes sperm whales very effective hunters(Burnham, R. Duffus, D., 2019). They have been recorded as being ready for hunting long before their prey is within visual range(Jebelli, Mustapha, Balbir, Nafiseh, 2018). Almost the entire anatomy of the sperm whale’s head is devoted to production and receival of sound. The oil sack called the melon, or spermaceti in sperm whales is connected to a series of channels and air sacs and something called junk, which helps cetaceans to focus the noise they can produce, especially the clicking noise as is often heard in recordings of whales, sometimes alongside beautiful melodies in social settings. The click system, the spermaceti and related organs, allows whales an extremely powerful echolocation system as well as communication abilities. This echolocation ability is found in all cetaceans except baleen whales. It is assumed that baleen whales find food via the sounds of thousands of small fish when they are feeding on plankton (Goldbogen, J. et. al. 2013). It is a mysterious and fine-tuned skill. These are the reasons that anthropogenic sound pollution in our oceans is a real issue. Our loud noise can disrupt communication, navigation, and hunting abilities for these creatures who depend on the ability to hear so much in their day-to-day survival (Hatch, L., et. al, 2012)

Anthropogenic noise, also known as noise pollution, comes in two forms: Transient noise, and background noise. There are multiple types of transient noise, they occur naturally in the forms of earthquakes and volcanic activity, and have been introduced artificially via geophysical airgun survey, acoustical oceanography sources, underwater explosions, and sonar (McDonald et. al., 1995). 

Sonar has been implicated in harm to the cetacean population since its introduction in the early twentieth century(Goldbogen, J. et. al. 2013). In the year 2000 there was a highly publicized string of mass strandings including Blainville's beaked whales (Mesoplodon densirostris) Cuvier's beaked whales (Ziphius cavirostris), and northern minke whales (Balaenoptera acutorostrata)(Bernaldo, 2019)(Walsh, S. 2019). The government determined that it likely happened due to sonar use in the area and this drew a lot of attention to the issue of sonar’s effects on cetaceans (Walsh, S. 2019). Sonar use has been subsequently linked to mass strandings of at least 7 other cetacean species since these findings in 2000 (Parsons, 2017). A particularly shocking mass stranding event in India included somewhere between 200-250 whales. Beaked whales have been observed utilizing evasive maneuvering in the presence of sound levels below 100 decibels and mass strandings have been caused by levels as low as 150 decibels (Parsons, 2017). Sonar can produce sounds up to 235 decibels.  This strongly suggests that naval activities; including sonar and seismic airguns, are detrimental to cetacean existence.  These are extreme effects of loud anthropogenic noise, all of this is not to even mention the effects of stress on these very sound-dependent animals. 

An extremely interesting study was done by Stephen J Trumble et. al. in 2018 wherein the team checked cortisol levels inner-ear laminae from 20 whales including humpback, blue, and fin whales (Trumble, S,. et al. 2018). The inner ear lamina forms seasonally like rings on a tree, and lends a snapshot of the whale’s physiological state during that period They found that whales that lived during WWII showed a departure from the usual stress level trends, as shown below.

Sonar became important during WWI but became effective and vital during WWII, Sonar technology that we use today was developed in the 1930s and was not used to full effect until WWII to detect submarines. Sonar usage, paired with increased explosions in the oceans and large ship activity that comes with warfare likely explains the half-decade spike in cortisol levels.  One would hope that we would have progressed past the need for such tools except maybe outside of well-planned scientific research.  

There is ample evidence that sonar does great harm to cetaceans. Yet what is being done is absolutely inadequate. The US navy base in San Diego has a policy of keeping a spotter to watch for cetacean breaching, and if they see any then the sonar systems are to be turned off. However this does not account for the fact that even the best spotter in the whole navy will not be able to see under the surface of the water at a distance. Suggestions have been made to limit sonar and explosion activity by military during mating seasons in specific areas but the navy have resisted, because it is inconvenient to have an hour ride away from the shore in order to do exercises(Walsh, S. 2019). However, shifting a shipping lane 15 miles over in the mediterranean reduced whale strikes by 95% in 2018 in the North Pacific (Gembe, S,. et al. 2019). No study was found to compare impact to cetaceans by extra CO2 levels given off by ships to direct strikes, however. It may be worthwhile to have our ships go a few hours out for training. They can sleep on the ships can’t they? They better be able to, those ships cost 100 million dollars.

Though it may be a simpler problem to begin to solve, it is nonetheless important, whale communication is affected by noise near global shipping routes. Large engines used in ships for global trade creates noise between 5 and 50 Hz and can disorient a whale. Such experiences have been observed causing higher rates of respiration in individuals, which brings them to the surface, which causes them to get hit or even worse, stranded on a beach, calling for help.  (McDonald et. al., 1995).  Ship strikes kill more than 80 whales on the west coast alone, annually (Pirotta, et. al. 2018). Strandings kill about 2000 cetaceans a year, and large events involving hundreds of individuals are not uncommon. (McDonald et. al., 1995).   

The great whales (Baleen and Sperm), basking sharks, and whale sharks, are notorious for being affected by global shipping noise (Pirotta, et. al. 2018). The Baleen whales come up to breath often, and the sharks exhibit basking behavior, the sperm whales can be found near the surface in revolving “daycare groups” for security. All three of these groups exhibit communication behaviors in the 5 to 50 Hz range which shippings vessels give off at a high decibel range (Pirotta, et. al. 2018).  The average depth of the ocean is about 12,00 feet (just over 2 miles), and the noise from the average shipping motor reverberates out 10km (about 6.2 miles) each direction in the ocean  (Pirotta, et. al. 2018). This means that  the options for escaping this shipping noise can sometimes be limited. Many cetaceans, narwhals especially, exhibit a violent flight response when faced with transient noise, which causes the brain to not get enough oxygen and explains why we have noticed on trackers that when a loud noise is present, some cetaceans lose their direction. This phenomenon has been widely observed in regards to seismic surveys and their impacts. 

Whales are known to avoid seismic surveys and have been observed doing so.  Seismic surveys use seismic airguns to search under the seafloor for natural gas. Seismic air guns produce sound at levels of 200 to 240 decibels in water and such explosions have been recorded at locations up to 4,000 kilometers from the source of the seismic survey(Dunlop, R. Noad, M. McCauley, R, et. al. 2017). Seismic surveys blanket a huge area in noise and have been observed displacing local cetaceans out of the area, disorienting migrating cetaceans so they end up swimming the opposite direction from where they were originally headed. Whales have been observed fleeing from seismic underwater activities such as earthquakes, it seems of all the anthropogenic noise seismic survey most closely mimics the sound of an earthquake (Croll et.al. 2001).

Perhaps this flight response is instinctual to ensure the cetacean’s safety in an earthquake scenario Another possibility is that cetaceans are aware of the possibility of decompression sickness near loud noise and want to avoid that. With the stress responses seen in cetaceans around loud noise, it probably causes some sort of pain that indicates trouble for an individual. 

When a cetacean is exposed to an especially loud noise, it can cause rapid decompression sickness, where a bubble of air develops in a blood vessel. They become disoriented and sick, stray into the shallows, end up beached, and eventually die due to dehydration, drowning when the high tide covers the blowhole, or collapsing under their own mass. About 2,000 cetaceans die a year due to strandings (Jebelli, Mustapha, Balbir, Nafiseh, 2018).  As they are dying they cry for help and other whales in the area, being such social creatures, come to their aid. Those whales, in an attempt to help the original whale, then also end up beached, sometimes by the hundreds. Even male sperm whales who were previously supposed to be solitary, have been observed in mass strandings, suggesting that there are deeper social relationships between them than we had previously assumed (Whitehead, H. 2018). Sonar and seismic surveys are notorious for causing these types of issues. Even if a whale gets too close to the shoreline, the situation can become very costly for them, as they have to swim faster to escape the tide coming in. This leads to lack of oxygen in the brain and potential loss of direction in the cetacean. This kind of damage can last for a long time and even cause permanent brain damage (Jebelli, Mustapha, Balbir, Nafiseh, 2018).

Humanity’s impact on cetacean kind is inexcusable. If we cannot be good shepherds of the earth for ourselves, we should at least be good shepherds for those who do not have a voice to raise on the issue. These wondrous animals have been around longer than we have been the “rulers of the planet” and if we disappeared tomorrow they would be better off for it. But we can greatly lessen our noise pollution impact to help our cetaceans to have the best shot at life possible. 

Luckily, this issue has been and is currently being well studied, and many solutions are absolutely feasible. We can manage our marine highways better and coordinate them with whale migration routes for minimal overlap, this will reduce impact of noise as well as whale strikes(Pirotta, et. al. 2018). We can retire the use of sonar except in responsible ocean mine clean-up efforts using spotters and passive sonar to make sure minimal harm is done. All militaries need to commit to impact studies as well as long-term observation, because the odds of seeing a whale in the area is 1 to 100(Parsons, 2017). We need to begin to understand our actual impact so that we can effectively alter course. The seismic airgun array issue may require more ingenuity, however. As a population we either need to find a better and quieter way to find undersea oil or more ideally, quit using oil all together as a species and opt for renewable resources. It may not be easy to gain the cooperation of the world on these issues, but it is an important step toward being good shepherds. It is one of many steps we will need to take to undo the damage that we have done to our ecosystems and biodiversity, and ensure a prosperous future on this planet.

Works Cited

Bernaldo de Quiro´s Y et al. 2019 Advances in research on the impacts of anti-submarine sonar on beaked whales. Proc. R. Soc. B 286: 20182533. 

Burnham, R. E., & Duffus, D. A. (2019). The use of passive acoustic monitoring as a census tool of gray whale (Eschrichtius robustus) migration. Ocean & Coastal Management, 105070. doi:10.1016/j.ocecoaman.2019.105070

Croll, D.A., Clark, C.W., Calambokidis, J., Ellison, W.T. and Tershy, B.R. (2001), Effect of anthropogenic low‐frequency noise on the foraging ecology of Balaenoptera whales. Animal Conservation, 4: 13-27. 

Dunlop Rebecca A., Noad Michael J., McCauley Robert D., Kniest Eric, Slade Robert, Paton David and Cato Douglas H. 2017The behavioural response of migrating humpback whales to a full seismic airgun arrayProc. R. Soc. B.2842017190120171901 

Gende SM, Vose L, Baken J, Gabriele CM, Preston R and Hendrix AN (2019) Active Whale Avoidance by Large Ships: Components and Constraints of a Complementary Approach to Reducing Ship Strike Risk. Front. Mar. Sci. 6:592. doi: 10.3389/fmars.2019.00592

Goldbogen Jeremy A., Southall Brandon L., DeRuiter Stacy L., Calambokidis John, Friedlaender Ari S., Hazen Elliott L., Falcone Erin A., Schorr Gregory S., Douglas Annie, Moretti David J., Kyburg Chris, McKenna Megan F. and Tyack Peter L. 2013Blue whales respond to simulated mid-frequency military sonarProc. R. Soc. B.2802013065720130657 (Goldbogen, J. et. al. 2013)

Guazzo, R., Helble, T., D’Spain, G., Weller, D., Wiggins, S., & Hildebrand, J. (2017). Migratory behavior of eastern North Pacific gray whales tracked using a hydrophone array. Retrieved April 16, 2021, from https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0185585

Hatch, L.T., Clark, C.W., Van Parijs, S.M., Frankel, A.S. and Ponirakis, D.W. (2012), Quantifying Loss of Acoustic Communication Space for Right Whales in and around a U.S. National Marine Sanctuary. Conservation Biology, 26: 983-994. 

Kishida, T., Thewissen, J., Hayakawa, T. et al. Aquatic adaptation and the evolution of smell and taste in whales. Zoological Lett 1, 9 (2015). https://doi.org/10.1186/s40851-014-0002-z 

McDonald, M. A., Hildebrand, J. A., & Webb, S. C. (1995). Blue and fin whales observed on a seafloor array in the Northeast Pacific. The Journal of the Acoustical Society of America, 98(2), 712–721. doi:10.1121/1.413565 

Parsons, E. (2017, August 30). Impacts of navy sonar on whales and dolphins: Now beyond a smoking gun? Retrieved April 16, 2021, from https://www.frontiersin.org/articles/10.3389/fmars.2017.00295/full

Pirotta, V., Grech, A., Jonsen, I. D., Laurance, W. F., & Harcourt, R. G. (2018). Consequences of global shipping traffic for marine giants. Frontiers in Ecology and the Environment. doi:10.1002/fee.1987 

Richardson, W. J., Würsig, B., & Greene, C. R. (1990). Reactions of bowhead whales, Balaena mysticetus, to drilling and dredging noise in the Canadian Beaufort Sea. Marine Environmental Research, 29(2), 135–160. doi:10.1016/0141-1136(90)90032-j 

Trumble, S.J., Norman, S.A., Crain, D. et al. Baleen whale cortisol levels reveal a physiological response to 20th century whaling. Nat Commun 9, 4587 (2018). https://doi.org/10.1038/s41467-018-07044-w 

Walsh, S. (2018, September 19). Whales and navy sonar. Retrieved April 16, 2021, from https://www.npr.org/2018/09/19/649432685/whales-and-navy-sonar

Whitehead, H. (2018). Sperm Whale. Encyclopedia of Marine Mammals, 919–925. doi:10.1016/b978-0-12-804327-1.00242-9 

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