The Impact on Marine Mammals by LeRoy French, NAUI A50
One of Jacques Cousteau’s first underwater films was entitled “The Silent World”. This was filmed almost a half century ago, and it labeled our underwater environment as a ‘silent world’. At the time this was true. Today, not so true.
Most marine mammals and fishes are very sensitive to sound. Noise travels long distances underwater and potentially prevents marine mammals and their young from finding their way. Some studies indicate that naval sonar affects large populations of whales. Seismic air guns used in gas exploration are also a large contributor to ocean noise. It has been shown that these air guns have affected fish at distances from over 500 meters to several kilometers. There are 40 to 80 percent fewer fish catches near seismic surveys.
Reef fish can be impacted by these various sounds as they rely on normal reef noises to help them select a suitable habitat.
However, whales seem to be the most vulnerable. They have been known to move away from feeding and breeding grounds along with altering their migration routes and in some cases have fallen completely silent. This means they are not communicating. Many have blundered into fishing nets and in some cases have collided with ships. This is most likely damage caused by “Ocean Noise”—Manmade “Ocean Noise”!
The three main culprits in this noise pollution are: the increase in commercial shipping, seismic surveys, and military sonar. All of these sounds make it increasingly difficult for whales and other marine mammals to communicate with song. This also leads to marine mammal strandings. Today shipping lanes follow coastal routes that whales have traced for millions of years. The result has led to beach strandings, collisions, and basically disorienting the whales so they lose their bearings. Here is an interesting statistic. Climate change is not helping the problem either. The acidification of oceans caused by rising temperatures reduces sound absorption by 40%, therefore allowing sound to travel even farther.
Why do Whales get Stranded?
This has been a huge mystery for many years. There have been hundreds of studies made on this interesting phenomenon. It is believed that whales use a magnetic field along with underwater topography to orient themselves. This means that any deviation to this field can cause confusion. It is not unusual for a beached whale after being returned to deeper water to later strand on the same beach from which it was freed.
What’s happening is that the whales’ reference points lead them to believe that they are heading to deeper water when in fact they are going toward the beach.
Aside from noise there are other factors involved. Whales may be hurt or sick. Also illness and parasites can affect their direction.
What should be noted is that when a whale is stranded and not able to get back into deeper water within a reasonable period of time it will die. Keep in mind that the whale’s body is supported by the sea; on land its body weighs it down, damaging internal organs and eventually causing suffocation.
Global Warming, Pollution, Plastic Bags, Runoff, the list seems endless. I know you are sitting there reading this and saying to yourself, what can I possibly do about “ocean noise?” What’s important is that you are made aware of how this pollution affects our ocean environment. You can help by supporting the different actions that help to protect our oceans and its inhabitants. Your voice is important.
Our underwater world is no longer a “Silent World,” just ask the animals that live there. You may, however, have to speak loudly.