“Another Hidden Crisis — Noise Pollution in the Ocean”
170th Ocean Forum

*This article was originally published in Japanese on August 27, 2020.
https://www.spf.org/spfnews/information/20200827.html
 
On May 14, 2020, the Ocean Policy Research Institute (OPRI) of the Sasakawa Peace Foundation (SPF) held the 170^th Ocean Forum "Another Invisible Crisis — Noise Pollution in the Ocean."
 
The event, which was led by the director of OPRI's Ocean Policy Research Department Dr. Tomonari Akamatsu and held online for the first time due to the COVID-19 pandemic, covered the situations surrounding ocean noise across all ocean-related fields. Topics included marine transport, maritime traffic, mineral resource exploration, and the development of ocean energy; the impact of ocean noise on marine life, such as fish and shellfish, and the marine environment; issues that organizations and countries including Japan should consider in light of both domestic and international research trends; and efforts for the future.
 
During opening remarks, Dr. Atsushi Sunami, then-president of OPRI (current president of SPF) stated, "the spread of COVID-19 highlights the fact that in addition to continuing our pursuit of sustainable development, modern society also must contend with the pressing challenges facing us today. The oceans are no exception, and I am renewing my belief that we must leverage our collective wisdom and actions to confront these challenges.” He also expressed his expectation to continue actively sharing information with stakeholders regarding ocean governance on topics including ocean noise while looking toward the emergence of a “new normal” after COVID-19.

Next, Dr. Akamatsu delivered a lecture explaining the ways that noise pollution, a problem that is invisible to the eye, is beginning to be highlighted internationally. While plastic waste released into the ocean is widely recognized around the world as a major problem, Dr. Akamatsu emphasized the importance of focusing on noise pollution, an invisible challenge that will continue in the future. "Humans have used the world’s oceans in various ways by building and operating wind turbines in offshore wind farms, engaging in trade, and pursuing resource exploration," he explained.
 
He also described the current issues surrounding the generation of offshore wind power, which has become a critical source of renewable energy, including the disturbance caused by installing the turbines and the noise pollution constantly emitted into the ocean caused by the rotating turbines. In fact, he noted that sound levels in the ocean are on the rise, introducing examples of measurements taken off the coast of California between the 1960s to the 1990s indicating that noise levels increased by a factor of three alongside significant economic development. "The fact that the noise levels were so high in the sea, where there should be no form of human life, shows how much humans are using the sea," he explained.
 
Dr. Akamatsu also remarked that while it is difficult to see 10 meters in front of you in the water, "sound travels about 5 times faster than in air, a fact that many marine organisms use to their advantage. However, this is the basic cause of the ocean noise problem." Acoustic propagation experiments conducted in the Indian Ocean and the Atlantic Ocean have demonstrated that sound can be transmitted at distances of up to 10,000 kilometers. Although researchers understand that underwater sounds can travel great distances, research has just begun on how this noise may affect marine life.
 
To explore how marine animals react to sound, Dr. Akamatsu introduced an experiment that examined how a small whale known as the grey whale responded to the U.S. Navy's low frequency active sonar, which is used for submarine detection. When the sound reached the whale, it clearly moved to avoid the source. However, the whale also continued to migrate and swim as it normally would when it was not bothered by the sound. In experiments with bottlenose dolphins, the animals experienced temporary hearing sensitivity loss after being exposed to a loud noise. In cases where animals are exposed to loud sounds for a long period of time, the sensitivity of hearing may continue to deteriorate, and if the sounds are too loud, the auditory nerve cells themselves may be destroyed. Dr. Akamatsu also pointed out that in cases where marine animals are dying due to loud sounds, the main culprit is the noise generated by destroying rocks with explosives for underwater construction.

Discussions on ocean noise are growing in prominence among international organizations. Ocean noise is mentioned in the United Nations Convention on the Law of the Sea (UNCLOS) and the United Nations Open-ended Informal Consultation Process (UNICPLOS), and the International Maritime Organization (IMO) is planning to develop and update non-compulsory guidelines for ship noise. The European Union and other organizations are also working to better understand ship noise and develop measures to reduce ocean noise. In light of these trends, Dr. Akamatsu argued that while noise pollution in the oceans has gained international attention over the last 10 years, the data is not sufficient and research should continue. For example, although data has been collected about how ocean noise threatens and harms red sea bream, these findings are limited to just one species, making data collection on other kinds of fish a critical area for future research.
 
On the other hand, Dr. Akamatsu pointed out that data continues to be collected to better understand marine animals’ capacity to perceive sounds. Especially for fish, the frequency band with adequate auditory sensitivity "almost matches the frequency of artificially emitted sound waves," so fish are easily impacted by the sound of ships and offshore wind farms. He also explained that animals such as dolphins and seals are highly sensitive to high frequencies, which often are similar to the sounds emitted by measuring instruments that use ultrasonic waves, such as sonar and fish finders. In addition, "although the hearing of large whales such as the baleen whale has rarely been measured directly, the anatomical characteristics of its inner ear indicate that it is highly sensitive to low-frequency sounds."
 
Another important factor regarding ocean noise is the level of sound that occurs naturally. The higher the level of surrounding noise (such as the sound of breaking sea waves or the clicking sound small shrimp make with their claws), the easier it is for additional sounds to mix with background noise, resulting in sounds not traveling very far. On the other hand, the lower the surrounding noise level, the greater the distance that the sound can reach, so "in a quieter environment, the amount of influence of sound increases," he explained. When it comes to “noise impact evaluation,” he explained that although it is easy to focus on the intensity of the noise source, "the original natural background noise level in the sea where the creature lives is very important."

Based on the impact of ocean noise on marine life and the current criteria for evaluation, Dr. Akamatsu discussed the work necessary to formulate policy proposals. These include: 1.) quantifying the behavioral and physiological responses to noise exposure, which is especially useful species for fisheries in Japan, 2.) formulating ocean sound measurement guidelines and visualizations to map the current sources of noise, 3.) estimating fluctuations in ecosystem services, which are the direct and indirect contributions of ecosystems to human well-being, due to the impact of noise pollution (effects on individual species and fluctuations in distribution and population, 4.) estimating the social costs and benefits of countermeasures to ocean noise, and 5.) proposing an acceptable level of social change that maximizes impact. In particular, the research group of the Marine Acoustic Society is currently studying the guidelines for measuring underwater sounds and is working to resolve future issues.
 
To conclude, Dr. Akamatsu stated that "ultimately, it is important that we weigh the social costs against the benefits to be gained from noise control measures, and make recommendations on the permissible level of social change that maximizes impact.”

See here for Dr. Akamatsu's profile: 
https://www.spf.org/en/about/staffs/0012.html