There is so much noise that sea creatures cannot hear …
Michelle Havlik dives into the Red Sea with an aquatic lecturer on a research expedition. (Photo: Michelle Havlik)
Sound is the sensory signal that travels the farthest in the ocean and is used by marine animals, from invertebrates to large whales, to interpret and explore their environment and to interact.
First published in the Daily Maverick 168 weekly newspaper.
The oceans have become considerably noisier since the industrial revolution. New research has shown how human-made noise negatively affects marine life forms, disrupting their behavior, physiology, reproduction and, in extreme cases, causing death.
Sound is the sensory signal that travels the farthest in the ocean and is used by marine animals, from invertebrates to large whales, to interpret and explore their environment and to interact. Drawing on 40 years of research, an international team of experts led by King Abdullah University of Science and Technology in Saudi Arabia has shown just how damaging noise pollution is.
In the research, published in early February in the journal Science, they explain that there are natural sounds such as wind blowing over the ocean, waves breaking, rain or hail falling on the surface of the sea, and gas bubbles that vibrate, rise and burst to the surface. There is the sound of earthquakes, underwater volcanoes and the activity of hydrothermal vents. And of course, the melting polar ice. There are the myriad of wonderful sounds animals make: from scratching crabs and sea urchins feeding to singing whales and dolphins, barking seals and even spawning fish.
Examples of human sound interference include seismic studies aimed at detecting the presence of oil and gas deposits under the seabed. The construction and operation of oil and gas infrastructure in the oceans is noisy. Offshore wind farms are just as bad during the construction phase and when the turbines are running.
Ships, scrapers and researchers
Fishing boats use “sounders” to search for schools of fish, and navies use active sonar over a range of frequencies to detect submarines and other targets.
Scientists say that “over the past 50 years, increased shipping has contributed to an estimated 32-fold increase in low-frequency noise present along major shipping routes. Ship noise is significant in many ocean regions, even far from major shipping lanes. “
“Technology that scrapes the ocean floor – whether it’s dredging the seabed, harvesting minerals or trawling fisheries – also generates low frequency noise. Dynamite fishing, designed to stun or kill reef fish for easy collection, remains a major source of blasting noise in Southeast Asia and coastal Africa, and the controlled detonation of WWII bombs dropped on the seabed continues to be a major source of disturbance and its destroyer in the North Sea. Explosions of mines, missiles and bombs during naval warfare or military exercises are also a source of its destroyer.
“On a small scale, even coastal recreational activities – such as small motorboats, swimming, scuba diving, surfing, boating, flying drones or fireworks – contribute,” said the ‘team.
Additionally, climate change directly affects the temperature, heat content and stratification of the ocean, with sound moving faster in warmer oceans.
Research shows that noise can interfere with the natural processing of the auditory signal by marine animals, called ‘masking’. The different noises overlap with the frequency band of animal hearing in the same way that we humans can’t hear a conversation at a loud party, so we start yelling at each other.
Signal masking disrupts cues of the presence of prey or predators, which can lead to loss of social cohesion and can lead to behavioral changes in marine animals.
Masking and attenuation
According to the team, navigation noise disrupts movement, foraging, socialization, communication and rest, and leads to increased mortality and a reduced ability to learn to avoid predators on future encounters. It is possible that some species will adapt, but there are gaps in the data on this and this may not be possible for many other species.
There are a limited number of studies testing the effectiveness of mitigation measures, but scientists say human stewardship needs regulatory frameworks designed to manage sound in exclusive economic zones and on the high seas, in order to promote the deployment of available technological solutions.
The simple act of reducing vessel speeds on major eastern Mediterranean shipping lanes from 15.6 to 13.8 knots resulted in an estimated 50% reduction in broadband noise from these vessels between 2007 and 2013.
Marine construction, especially for offshore wind farms, gets results with noise dampening technology. Acoustic barriers such as bubble curtains and noise reduction ducts have been introduced in some European wind farms.
The team hopes the research will prompt national and international policies to regulate marine noise, which the researchers say is “the neglected elephant in the room of global ocean change.” DM168
This story first appeared in our Daily Maverick 168 weekly newspaper which is available for free to Smart Pick n Pay shoppers at these Pick n Pay stores.