Introduction

Any activity that occurs under the sea has the potential to generate noise pollution that disrupts marine animals. The most significant sources of damaging noise are seismic surveys, blasting, construction and sonar devices. Animals that are the most sensitive to underwater noise are those that use echolocation or sonar for feeding and navigation. Dolphins appear to be particularly sensitive to high-pitched noises, such as those caused by pile-driving or drilling, and can be affected from distances of up to 1-2 km. Whales tend to be affected by deeper sounds. Their behaviour has been shown to be influenced by noises from airgun operations up to 7 km away, and to be adversely affected by such noises occurring within 3 km. Noise pollution in Darwin Harbour is a concern for Australian Snubfins, Indo-Pacific Humpback Dolphins and Indo-Pacific Bottle-nosed Dolphins.

Noise pollution

Photo: © Carol Palmer

Impacts

Sub-marine noises can disrupt communication between marine mammals. Loud and/or persistent noises can deafen whales and dolphins, and cause haemorrhaging or even death. Whales and dolphins are known to avoid or leave noisy areas. Unable to migrate, calving animals may suffer deafness, disorientation or death. Some whale strandings have also been attributed to underwater noise pollution.

Management

Make every effort to minimise exposure of dolphins and whales to detrimental noise. When undertaking any activity that involves creating sub-marine noise, check whether the activity will require a permit from the Australian Government. If so, follow the procedures stipulated by the permit. Even if permits are not required, following these procedures will help minimise any negative impact. In dolphin or whale habitat, surveys should be undertaken to ascertain if any animals are present within range of noise sensitivity; and any activity should be delayed until these animals have departed. No significant noises should be produced where dolphins are calving. Passage of sound may be reduced by buffering the source with a curtain of air bubbles.

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