Ocean traffic noise in the context of natural ambient noise in impacts on marine mammals.

Abstract

Traffic noise, the background noise from distance shipping, is the most widespread anthropogenic component of ambient noise. There has been concern for decades that traffic noise may be limiting the ability of marine mammals to communicate, but there is little direct evidence of actual impacts or the significance of these on the well being of populations, possibly because of the difficulties in obtaining such evidence. This paper compares traffic noise with natural ambient noise in the same frequency band. Marine mammals have evolved to cope with the range of levels in natural ambient noise. It draws on studies from areas near Australia where there is a wide range in traffic noise levels. In some areas, traffic noise is so low that it is possible to determine the range of natural ambient noise in the frequency band where traffic noise usually dominates. In other areas, traffic noise reaches levels similar to some of the high levels observed near North America. Humpback whales that migrate along the east coast of Australia are subject to high levels of traffic noise and noise from passing ships, but there seems to be little impact on the whales at the population level.