Sound travels faster in water than in air. In the ocean’s salt water sound waves can travel quickly for hundreds or even thousands of miles along “sound channels” – while shallow channels tend to be transient, the deep sound channels created by the temperature and pressure gradients of ocean waters are quite stable. Many marine mammals (particularly whales and dolphins) communicate through sound over long distances and have very sensitive hearing and other sound receptors; they are very sensitive to sounds and vibrations in the ocean and some use echolocation to navigate through the ocean.
For decades conservation biologists and activists have worked to reduce the noise hazards to these animals and other marine species (like turtles) from commercial shipping, military sonar use (which creates a loud screeching sound underwater) and the very loud commercial activities using seismic guns and blasting to perform surveys in the ocean. After decades of advocacy, some limits were eventually imposed in this country on sonar testing and seismic blasting (but it has expanded elsewhere across the globe). The constant noise from commercial shipping has already decreased the ability of whales to communicate particularly near shipping routes and coastlines, and shipping continues to increase across the globe and into southern waters where shipping had been more sparse just a decade ago.
Now even some of the few protective limits on seismic testing and blasting are being weakened or eliminated by the current administration. First, the Navy announced in August that it plans to weaken limits and increase the area for active sonar use and testing in the Pacific Ocean from California to Hawaii. With fewer areas being placed off limits unless whales or dolphins are actually seen in the area where they are running tests, the problem is, whales are hard to detect visually and could already be adversely impacted by the sonar long before they were “seen” by the Navy. The Navy’s own studies show that the noise from sonar testing can disrupt feeding and breeding activity and also cause marine mammals to rise too quickly to get away from the sound, causing internal bleeding or death. The impact would be hard to trace and unlikely to come to light until long after the damage is done. Earlier plans were challenged in court, this will likely be challenged as well once it is finalized.
Second, after more than 30 years of protections being in place, in late November the administration approved a permit to allow seismic blasting to search for oil along the east coast from Maryland to northern Florida, a permit that has been denied by the last administration. Seismic surveys use air guns to blast the ocean floor with acoustic waves every 10 seconds to map what’s underneath. Up to 48 air guns can be arranged in a rectangle, shooting blasts directly down that can be as high as 250 decibels—like dynamite going off every 10 seconds. The impacts to whales and other marine mammals from this blasting could be devastating. The way we measure hearing damage is flawed and based on one-time events but this would be day after day, week after week. Every 10 seconds. The question shouldn’t be just: `Is it so loud that it is permanently damaging the whale’s ears?’ but rather, “Is this undermining the whale’s ability to thrive.” A coalition of environmental groups filed a lawsuit in early December 2018, to try and stop the blasting.
The spectacular (but gruesome) 1956 underwater documentary from oceanographer Jacques-Yves Cousteau and director Louis Malle was called “The Silent World”, but it is now “the very noisy ocean”. You might want to check out an excellent documentary on the ocean noise issues from 2016, “Sonic Sea” http://sonicsea.org/ (I had to pay to watch it on line but maybe you can get it at your library?) And you can check out a short video on the sound issue with lovely water color paintings here https://youtu.be/GFPTpbSFr74