Assessment of acoustic impacts on marine animals

Marine animals use sound for communication, navigation, predator avoidance, and prey detection. Thus, acoustic energy accompanying military exercises, transportation and commercial shipping, geophysical research, and development of offshore energy resources has potential to affect their existence. Many challenges exist in determning effects of sound exposure on multiple species, creating underwater source-path-receiver models, and implementing effective mitigation to protect against acoutic impacts. Fortunately, in the last 10-15 years advances in electrical and computing technologies have yielded new research tools directly applicable for data collections to study aquatic animals in their natural habitats rather than only those held in captivity. Now portable systems to record physilogically evoked, asuditory potentials in response to sound enable measurement of hearing in many species in the wild. Miniaturized underwater acoustic tags temporarily attached to animals to record their movement, vocalizations, echolocation, and surrounding acoustic environment reveal diving and foraging behavior of large whales. Mobile and fixed passive acoustic monitoring systems automatically detect and characterize biological and physical features of an ocean area without adding any acoustic energy tot he environment. Data collection needed to understand the potential acoustic impacts and to comply with environmental laws is ongoing and expensive, but with these new technologies progress is being made to minimize risks associated with sound generated by human activities in the ocean. This article provides a brief review of acoustic sources that are of concern, technologicval tools now being used to elucidate relationships between marine animals and their acoustic environment, and data gaps that remain to be filled.