Hearing is believing

Dr. Leigh Torres, Geospatial Ecology of Marine Megafauna Lab, Marine Mammal Institute, Oregon State University

Dr. Holger Klinck, Bioacoustics Research Program, Cornell Lab of Ornithology, Cornell University

For too long the oil and gas industry has polluted the ocean with seismic airgun noise with little consequence. The industry uses seismic airguns in order to find their next lucrative reserve under the seafloor, and because their operations are out of sight and the noise is underwater many have not noticed this deafening (literally¹) noise. As terrestrial and vision-dependent animals, we humans have a hard time appreciating the importance of sound in the marine environment. Most of the ocean is a dark place, where vision does not work well, so many animals are dependent on sound to survive. Especially marine mammals like whales and dolphins.

But, hearing is believing, so let’s have a listen to a recording of seismic airguns firing in the South Taranaki Bight (STB) of New Zealand, a known blue whale feeding area. This is a short audio clip of a seismic airgun firing every ~8 seconds (a typical pattern). Before you hit play, close your eyes and imagine you are a blue whale living in this environment.

Now, put that clip on loop and play it for three months straight. Yes, three months. This consistent, repetitive boom is what whales living in a region of oil and gas exploration hear, as seismic surveys often last 1-4 months.

So, how loud is that, really? Your computer or phone speaker is probably not good enough to convey the power of that sound (unless you have a good bass or sub-woofer hooked up). Industrial seismic airgun arrays are among the loudest man-made sources² and the noise emitted by these arrays can travel thousands of kilometers³. Noise from a single seismic airgun survey can blanket an area of over 300,000 km², raising local background noise levels 100-fold⁴.

Now, oil and gas representatives frequently defend their seismic airgun activities with two arguments, both of which are false. You can hear both these arguments made recently in this interview by a representative of the oil and gas industry in New Zealand defending a proposal to conduct a 3 month-long seismic survey in the STB while blue whales will be feeding there.

First, the oil and gas industry claim that whales and dolphins can just leave the area if they choose. But this is their home, where they live, where they feed and breed. These habitats are not just anywhere. Blue whales come to the STB to feed, to sustain their bodies and reproductive capacity. This habitat is special and is not available anywhere else nearby, so if a whale leaves the STB because of noise disturbance it may starve. Similarly, oil and gas representatives have falsely claimed that because whales stay in the area during seismic airgun activity this indicates they are not being disturbed. If you had the choice of starving or listening to seismic booming you might also choose the latter, but this does not mean you are not disturbed (or annoyed and stressed). Let’s think about this another way: imagine someone operating a nail gun for three months in your kitchen and you have nowhere else to eat. You would stay to feed yourself, but your stress level would elevate, health deteriorate, and potentially have hearing damage. During your next home renovation project you should be happy you have restaurants as alternative eateries. Whales don’t.

Second, the oil and gas industry have claimed that the frequency of seismic airguns is out of the hearing range of most whales and dolphins. This statement is just wrong. Let’s look at the spectrogram of the above played seismic airgun audio clip recorded in the STB. A spectrogram is a visual representation of sound (to help us vision-dependent animals interpret sound). Time is on the horizontal axis, frequency (pitch) is on the vertical axis, and the different colors on the image indicate the intensity of sound (loudness) with bright colors illustrating areas of higher noise. Easily seen is that as the seismic airgun blasts every ~8 seconds, there is elevated noise intensity across all frequencies (bright yellow, orange and green bands). This noise intensity is especially high in the 10 – 80 Hz frequency range, which is exactly where many large baleen whales – like the blue whale – hear and communicate.

In the big, dark ocean, whales use sound to communicate, find food, and navigate. So, let’s try to imagine what it’s like for a whale trying to communicate in an environment with seismic airgun activity. First, let’s listen to a New Zealand blue whale call (vocalization) recorded in the STB. [This audio clip is played at 10X the original speed so that it is more audible to the human hearing frequency range. You can see the real time scale in the top plot.]

Now, let’s look at a spectrogram of seismic airgun pulses and a blue whale call happening at the same time. The seismic airgun blasts are still evident every ~8 seconds, and the blue whale call is also evident at about the 25 Hz frequency (within the pink box). Because blue whales call at such a low frequency humans cannot hear their call when played at normal speed, so you will only hear the airgun pulses if you hit play. But you can see in the spectrogram that five airgun blasts overlapped with the blue whale call.

No doubt this blue whale heard the repetitive seismic airgun blasts, and vocalized in the same frequency range at the same time. Yet, the blue whale’s call was partially drowned out by the intense seismic airgun blasts. Did any other whale hear it? Could this whale hear other whales? Did it get the message across? Maybe, but probably not very well.

Some oil and gas representatives point toward their adherence to seismic survey guidelines and use of marine mammal observers to reduce their impacts on marine life. In New Zealand these guidelines only stop airgun blasting when animals are within 1000 m of the vessel (1.5 km if a calf is present), yet seismic airgun blasts are so intense that the noise travels much farther. So, while these guidelines may be a start, they only prevent hearing damage to whales and dolphins by stopping airguns from blasting right on top of animals.

So, what does this mean for whales and other marine animals living in habitat where seismic airguns are operating? It means their lives are disturbed and dramatically altered. Multiple scientific studies have shown that whales change behavior⁵, distribution⁶, and vocalization patterns⁷ when seismic airguns are active. Other marine life like squid⁸, spiny lobster⁹, scallops¹⁰, and plankton¹¹ also suffer when exposed to airgun noise. The evidence has mounted. There is no longer a scientific debate: seismic airguns are harmful to marine animals and ecosystems.

What we are just starting to study and understand is the long-term and population level effects of seismic airguns on whales and other marine life. How do short term behavioral changes, movement to different areas, and different calling patterns impact an individual’s ability to survive or a population’s ability to persist? These are the important questions that need to be addressed now.

Seismic airgun surveys to find new oil and gas reserves are so pervasive in our global oceans, that airgun blasts are now heard year round in the equatorial Atlantic^{3, 12}. As reserves shrink on land, the industry expands their search in our oceans, causing severe and persistent consequences to whales, dolphins and other marine life. The oil and gas industry must take ownership of the impacts of their seismic airgun activities. It’s imperative that political, management, scientific, and public pressure force a more complete assessment of each proposed seismic airgun survey, with an honest evaluation of the tradeoff between economic benefits and costs to marine life.

Here are a few ways we can reduce the impact of seismic airguns on marine life and ecosystems:

• Restrict seismic airgun operation in and near sensitive environmental areas, such as marine mammal feeding and breeding areas.
• Prohibit redundant seismic surveys in the same area. If one group has already surveyed an area, that data should be shared with other groups, perhaps after an embargo period.
• Cap the number and duration of seismic surveys allowed each year by region.
• Promote the use of renewable energy sources.
• Develop new and quieter survey methods.

Even though we cannot hear the relentless booming, this does not mean it’s not happening and harming animals. Please listen one more time to 1 minute of what whales hear for months during seismic airgun operations.

More information on seismic airgun surveys and their impact on marine life:

Boom, Baby, Boom: The Environmental Impacts of Seismic Surveys

A Review of the Impacts of Seismic Airgun Surveys on Marine Life

Sonic Sea: Emmy award winning film about ocean noise pollution and its impact on marine mammals.

Atlantic seismic will impact marine mammals and fisheries

References:

1. Gordon, J., et al., A review of the effects of seismic surveys on marine mammals. Marine Technology Society Journal, 2003. 37(4): p. 16-34.
2. National Research Council (NRC), Ocean Noise and Marine Mammals. 2003, National Academy Press: Washington. p. 204.
3. Nieukirk, S.L., et al., Sounds from airguns and fin whales recorded in the mid-Atlantic Ocean, 1999–2009. The Journal of the Acoustical Society of America, 2012. 131(2): p. 1102-1112.
4. Weilgart, L., A review of the impacts of seismic airgun surveys on marine life. 2013, Submitted to the CBD Expert Workshop on Underwater Noise and its Impacts on Marine and Coastal Biodiversity 25-27 February 2014: London, UK. .
5. Miller, P.J., et al., Using at-sea experiments to study the effects of airguns on the foraging behavior of sperm whales in the Gulf of Mexico. Deep Sea Research Part I: Oceanographic Research Papers, 2009. 56(7): p. 1168-1181.
6. Castellote, M., C.W. Clark, and M.O. Lammers, Acoustic and behavioural changes by fin whales (Balaenoptera physalus) in response to shipping and airgun noise. Biological Conservation, 2012. 147(1): p. 115-122.
7. Di lorio, L. and C.W. Clark, Exposure to seismic survey alters blue whale acoustic communication. Biology Letters, 2010. 6(1): p. 51-54.
8. Fewtrell, J. and R. McCauley, Impact of air gun noise on the behaviour of marine fish and squid. Marine pollution bulletin, 2012. 64(5): p. 984-993.
9. Fitzgibbon, Q.P., et al., The impact of seismic air gun exposure on the haemolymph physiology and nutritional condition of spiny lobster, Jasus edwardsii. Marine Pollution Bulletin, 2017.
10. Day, R.D., et al., Exposure to seismic air gun signals causes physiological harm and alters behavior in the scallop Pecten fumatus. Proceedings of the National Academy of Sciences, 2017. 114(40): p. E8537-E8546.
11. McCauley, R.D., et al., Widely used marine seismic survey air gun operations negatively impact zooplankton. Nature Ecology & Evolution, 2017. 1(7): p. s41559-017-0195.
12. Haver, S.M., et al., The not-so-silent world: Measuring Arctic, Equatorial, and Antarctic soundscapes in the Atlantic Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 2017. 122: p. 95-104.