This article is part two of a two part series on how anthropogenic noise affects marine life. Part one discussed the sources of anthropogenic noise in the oceans. This article details the different ways that marine life is affected by anthropogenic noise.
Communication
Anthropogenic noise (caused by human activities) in the oceans can occur at a frequency that makes cestaceans unable to communicate with each other. The noise can fully drown out the sounds of communication for whales, dolphins, and porpoises (collectively known as cetaceans). Lack of communication makes unable to socialize, detect food sources, or detect predators. Scientist's have observed that Beluga Whales stop communicating for hours to days after exposure to low frequency noise.
Migration
Anthropogenic noise can cause whales and dolphins to change their migration paths and avoid areas where they normally inhabit.
Cetaceans have been observed going off their normal migratory path to avoid exposure to anthropogenic noise. Researchers have observed Gray Whales detouring off their migratory path to avoid noise caused by offshore oil drilling. Common Dolphins, Bowhead Whales, Sperm Whales and Humpback Whales purposely stay away from noise caused by seismic surveys conducted for oil exploration. Seismic surveys produce extremely loud sounds that can cause hearing loss in marine life.
Hearing Loss
Cetaceans that are exposed to anthropogenic noise can experience hearing damage or full hearing loss. Some hearing loss is a result of long term exposure to low levels of noise. Some hearing loss can be caused instantly by exposure to high levels of noise. Hearing loss can affect a cestacean's ability to communicate, feed, protect themselves from predators, and navigate.
Two Sperm Whales who had experienced hearing loss caused by anthropogenic noise exposure, as evidenced by damage to their inner ears, were unable to hear a cargo ship coming towards them and were hit and killed by the ship as a result.
Disorientation
When cetaceans are exposed to extremely loud noises, they can become disorientated. The loud noises can cause the animals to attempt to flee in desperation to escape from the sounds that are causing them pain. Disorientated and unable to find relief from the far stretching noise and unable to use their sonar to navigate because of the noise pollution, they sometimes beach themselves onto shore.
Deaths
Increasing amounts of whales and dolphins are dying as a result of exposure to anthropogenic noise. Examinations of beached cetaceans have shown hemorrhages in their brains and ears as evidence of damage caused by exposure to anthropogenic noise. It is impossible to know how many deaths are caused by anthropogenic noise because not all marine life that dies from exposure, beaches themselves. Some die out in the sea and sink to the bottom of the ocean floor.
Recent strandings of beached cetaceans have caused concern over the wide spread harm caused to dolphins and whales by exposure to anthropogenic noise.
There have been many recorded cases of marine mammals beaching themselves during naval exercises and maneuvers. The following list details some of the recorded cases, most of which resulted in death to the marine animals.
Canary Islands
1989 - 20 whales
1991 - 2 whales
2002 - 18 Beaked Whales
2004 - 4 Beaked Whales
West Coast of Greece
1996 - 12 Cuvier Beaked Whales
Virgin Islands
1999 - 4 Beaked Whales
Vieques
2000 - 1 Beaked Whale
Madeira
2000 - 3 Beaked Whales
Washington State
2003 - Approximately 11 Harbor Porpoises
Alaska
2004 - Approximately 6 Beaked Whales
Hanalei Bay Hawaii
2004 - Approximately 200 Melon Headed Whales crowded into the shallow bay in an attempt to escape noise from a naval exercise. All but one of the Melon Headed Whales were guided back out to sea by volunteers.
Outer Banks of North Carolina
2005 - 34 whales
Zanzibar
2006 - Approximately 600 dolphins
Resources
How Anthropogenic Noise Affects Marine Life
Anthropogenic noise in oceans is increasing at an alarming rate. Research has proved that anthropogenic noise is causing detrimental effects on marine life. Anthropogenic noise has shown to be responsible for behavioral changes, hearing loss and death in cetaceans.