Underwater Noise: Sources and Effects on Marine Life

Traveling underwater much faster than in air and covering much greater distances, sound provides an excellent means for rapid information acquisition and exchange. Consequently, sound is used by many marine organisms forcommunication purposes, food location, and for orientation. The frequency of sound affects its propagation capabilities and often defines its purpose and use. Numerous sound sources of natural physical, biological, and anthropogenic origin constitute the overall ambient noise in the sea. Human inputs into the marine environment have been of particularly high interest recently as it was found to affect a wide range of marine species. Responses to noise not only depend on received sound levels, its frequency and duration of animals’ exposure to it, but are also influenced by the state of the animals exposed, novelty of sound as well as the spatial relations between the sound source and the animals. Responses to noise may also differ among species according to their hearing capabilities and their sensitivities to detect sound pressure and/or particle motion. Much attention has been dedicated to the effects of noise on hearing and communication systems of acoustically active species, although recent studies have also indicated possibilities of noise causing other indirect effects through alterations of physiology and behavior. In the long term, the introduction of anthropogenic sound in the sea can cause alterations of the acoustic environment that can negatively affect the persistence of populations and species, especially when combined with other environmental stressors.