Impacts of Ocean Noise on Marine Life

Impacts on Marine Mammals

Marine mammal strandings are the most visible impacts of anthropogenic noise. Such incidents, however, only give a snapshot of the real problem, since affected animals may not beach and some may suffer long term effects that are not measurable. Population level impacts have occurred in stranding incidents, such as the mass stranding of beaked whales in 2000 in the Bahamas. This stranding - caused by the passage of a single U.S. Navy ship using active mid-frequency sonar - resulted in 17 deaths and the loss of a well-studied population of beaked whales from the area.

Negative responses to anthropogenic noise have been demonstrated in at least 27 species of marine mammals in scientific studies. Effects can include:

  • Mortality or serious injury caused by hemorrhaging around the brain, air cavities, lungs and other organs;
  • Mortality or serious injury caused by the formation of nitrogen bubbles in the bloodstream, leading to embolism;
  • Temporary or permanent loss of hearing, impairing an animal’s ability to perform essential life functions, such as communication, avoiding predators, avoiding vessel traffic, finding mates and catching prey ;
  • Stranding caused by the above factors;
  • Avoidance behavior, which can lead to abandonment of habitat or migratory pathways and disruption of mating, feeding or nursing;
  • Aggressive behavior, which can result in injury;
  • Masking of biologically meaningful sounds, such as the call of predators or potential mates; and
  • Depletion of prey species.

Impacts on Fish and Other Marine Species

Intense ocean noise damages fish and, consequently, fisheries. Research so far has indicated reactions to noise in 21 species of fish. Since anthropogenic ocean noise can travel hundreds of miles from its source, the potential impact to fisheries from domestically unregulated foreign noise activities is immense. This could have significant effects on national economies, commercial fisheries and local fishing communities. Harmful effects include:

  • Extensive damage to fish ears and hearing;
  • Catch rates reduced 40–80% and fewer fish near seismic surveys reported for cod, haddock, rockfish, herring, sand eel and blue whiting;
  • Disruption in schooling structure, swimming behavior, and, possibly, migration in bluefin tuna;
  • Secretion of stress hormones in several fish species in the presence of shipping noise;
  • Alteration of gene expression in the brain of codfish following airgun exposure;
  • A significant increase in heart rate in embryonic clownfish with exposure to noise;
  • Negative impacts on sand eels from airguns;
  • Avoidance behavior in capelin and eels when exposed to noise;
  • A reduction in growth and reproduction in brown shrimp exposed to noise;
  • Bruised organs, abnormal ovaries, smaller larvae, delayed development and stress in snow crabs when exposed to seismic noise; and
  • Increased food consumption and histochemical changes in lobster after exposure to seismic noise.