Underwater Noise and Marine Animals
To hear a recording of an underwater grinder, please follow this link at SubAcoustech.
This is the sound of an underwater grinder manually operated by a diver. The sound from the computer reached your ears by traveling through the air, which compresses and acts like a cushion for the sound waves.
Now imagine hearing this underwater, where sound travels faster and farther in an incompressible substance. Imagine being subjected to this kind of noise and pressure waves for seconds, minutes, and hours – with virtually no place to go or hide from the noise. This is what marine animals experience whenever sound waves from underwater noise hit them.
To hear a recording of a geophysical survey airgun, please follow this link at SubAcoustech.
Underwater noise from various human and construction activities have been implicated several times in the injury and death of nearby marine animals in the area. Noise from underwater explosions, construction (dredging, piling, drilling, etc.), passage of ships and use of sonar all produce underwater sound waves and pressure waves. When powerful and intense enough, these may cause harm and even kill marine animals nearby. Injuries to auditory organs, lung damage, and internal hemorrhage are only some of the injuries sustained by marine animals and marine mammals in particular after being exposed to powerful underwater sound and pressure waves. It has long been thought that only marine mammals like whales and dolphins are affected by such waves, since they use natural sonar to navigate and hunt. But increasingly, evidence is stocking up that even other kinds of marine animals are vulnerable. A study reports that cephalopods like giant squids have been found to sustain bruised muscles and internal organ lesions after being exposed to low intensity, low frequency sound underwater.
To hear a recording of underwater piling (750m from source), please follow this link at SubAcoustech.
In a National Geographic article, the case of the San Francisco-Oakland Bay Bridge was cited as an example of pressure waves from underwater construction affecting and killing marine life. Dead fish appeared shortly after CalTrans (California Department of Transportation) conducted an early test of driving piles into the seabed for their project. The consulting marine biologist of the project, Bud Abbott, had warned that the pressure waves from the piling might affect both fish and seals nearby. Further examination revealed that the swim bladders of the collected dead fish have ruptured and their kidneys were extensively damaged. Marine biologist Bud Abbott concludes that the pressure waves have compressed the air inside the swim bladder and caused it to rupture after quickly expanding again. In response to this, CalTrans installed walls of air bubbles directly against the piles to help reduce the impact of the waves and observed that the overall fish mortality was reduced. In addition, no delayed mortalities occurred beyond 69 meters from the piling.
To see a video of a group of orcas and a Navy ship using sonar for five hours in the area, please follow this link at Earthjustice.org.
Much controversy has been made about the use of sonar by armies of different nations around the world, the Navy included. Significant circles and voices in the scientific community believe that sonar directly affects marine mammals and their health. Subacoustech shares an excellent collection of reports and studies regarding the subject of underwater acoustics. These include experiments of human divers and even non-marine animals being submerged and subjected to different levels and intensities of underwater sound waves, and the effects the subjects experienced. These also document the behavioral effects of underwater sound waves to marine animals, which include avoidance reaction and even separation of mother and cub whales. Repeated incidents of mass strandings and beachings of different species of whales happening when there was naval activity in the area involving sonar use invariably point to this conclusion. Yet the military maintains that the use of sonar is not directly responsible for the injuries and deaths of the marine animals. In a recent video uploaded in the U.S. Navy Energy and Environment Channel or NavyEnergyEnviro, Dr. Darlene Ketten, Senior Scientist of Woods Hole Oceanographic Institute (a research institute supported and sponsored by the military) puts it directly:
“In the case of the animals that have stranded, that have died, and we’ve collected the ears and heads from these animals to examine what evidences therefore and hearing problems or other kinds of trauma. And also what can I tell them about whether not there is evidence that there were sound related impacts in the bodies.
I can finally after several years of research say we do not see acoustic trauma. It wasn’t the sound of the sonars per se in any of the animals that have been examined not just by me but by also other researchers who have looked at animals that are stranded in their vicinity. We’re not seeing direct acoustic impacts. So it’s not the sonar, there’s some other behavioral component to this. ”
– Dr. Darlene Ketten, Navy Sonar and Environmental Stewardship
This is in direct contrast to several reports and findings on the harmful effects of sonar to marine animals which include gross damage of auditory organs, body tissue damage, and interference in communication, navigation, and hunting. MarineConnection.org, Ocean Mammal Institute, LFAS, WorldWideWhale, and Orca Network are only some of the groups who directly hold use of sonar as responsible for these marine animals injuries and mortalities. In the video, the emphasis on the use of sonar as crucial to Navy training and in extension, the nation’s safety, is reiterated. The Navy, despite criticism, continues to use sonar in training.
To see Orca Network’s Board President Howard Garrett narrate the previous video of orcas and sonar use, please follow this link.
The video mentioned above shows a group of orcas changing direction after the USS Shoup used sonar. Howard Garrett of Orca Network points out that the orcas tried to stay on the surface of the water, the only place where the intensity of the noise is lessened. Sonar use and whale beachings have been linked for years but only a few individuals and groups had the courage to say boldly that sonar is directly harming the animals. If these findings and reports are true, downplaying and denying sonar’s harmful effects to marine animals will only impede the search and development of an appropriate solution that will address both sides of the problem (marine animals’ welfare and necessary military training).
In 1956, Jacque-Yves Costeau gave the world Le Monde du silence or The Silent World. It was a stunning visual revelation of the beauty of the underwater world. Following a 900% increase in underwater ambient noise from 1950s to 1970s, it might not only be a noisy world, but a lethal one as well.
Photo Credit: Some rights reserved by Wessex Archaeology on Flickr.
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