How does anthropogenic (human-generated) sound affect marine animals? The ocean is full of both natural and anthropogenic sources of sound (see What are common underwater sounds?). Much attention has recently been focused on anthropogenic sources of sound in the oceans and their potentially harmful effects on marine animals. This has become a topic of increasing controversy, especially regarding marine mammals.

Marine mammals face threats from many different human activities, including fishing, habitat destruction, ship strikes, whaling, and sound production. Of these threats, fisheries bycatch kills the most marine mammals. Globally, it is estimated that more than 650,000 marine mammals are killed annually by being accidentally caught in fishing nets (Read et al., 2006). Although there have only been a small number of deaths of marine mammals associated with underwater sound, sound is included here as a threat because we know that it can affect marine mammals in a number of ways.

Researchers (1, 2) suggest that increased background noise and specific sound sources might impact marine animals in several ways. The effects vary depending upon the intensity and frequency of the sound, and other variables.

1. cause marine animals to alter their behavior
2. prevent marine animals from hearing important sounds (masking)
3. cause hearing loss (temporary or permanent) or tissue damage in marine animals

The following sections discuss effects that have been discovered using rigorous scientific methods and are published in the scientific literature.

A number of factors affect the impact of sounds on marine animals. These include the sound level, frequency, and other characteristics of the sounds; the hearing sensitivity, age, sex, and behavior of the animals; and the environmental conditions under which the animals experience the sound. It is also not clear how important these impacts are to the well being of the animals and their populations.

Current knowledge about the effects of sound on marine animals is based on research on a small number of animals and is complicated by differences between the individual animals. It is difficult and expensive to study marine animals. Much more scientific research is needed to fully understand the effects of anthropogenic sounds on marine animals. The following sections discuss what has currently been discovered.

For more information on how specific marine animals are affected by sound, use the following links:
Marine Mammals	Fish