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Overview Of The Impacts Of Anthropogenic Underwater Sound In The Marine Environment

Study Status: 
Completed
Princple Investigator Contact Information: 

Name: Gordon Hastie

Email: gdh10@st-andrews.ac.uk

Project Description: 

This paper presents the Overview of the Impacts of Anthropogenic Underwater Sound in the Marine Environment in the modular approach. Besides this introductory chapter, it is comprised of the following seven modules: 2) Background on underwater sound, 3) Background on impacts of sound on aquatic life, 4) Marine construction and industrial activities, 5) Shipping, 6) Sonar, 7) Seismic surveys, and 8) Other activities.

Project Aims: 

To provide an overview of anthropogenic underwater sound in the marine environment

Project Progress: 

Completed

Key Findings: 

Avoidance behavior by marine mammals can be expected to occur in response to several of the ‘other’ noise sources. However, ranges over which animals might be impacted will depend on the species, and the respective noise source. Large-scale habitat exclusion of odontocetes (a non-target species) has been demonstrated in response to commercially available acoustic harassment devices (AHDs) and should be considered a potential concern (if no mitigation measures are implemented). Although there is the potential that some pingers could exclude porpoise from their habitat, it should be highlighted that avoidance responses do not seem to extend over more than a few hundred meters from the device (3, 8). Therefore, the benefits of reducing lethal by-catch may outweigh the impact on behavior in some populations and habitats. Due to their high frequency content, both AHDs and pingers are less likely to affect fish behavior, except for individuals within the immediate vicinity of the device. Ocean research studies and low-frequency fish deterrents have a clear potential to influence the behavior of large whales (e.g. baleen whales) and pinnipeds. However, with respect to ocean research activities, monitored responses during experiments did not always seem to be overt (1, 4). Similarly, some studies failed to show a clear effect of ocean research studies on the behavior of fish. However, captive experiments on fish may indicate that some effects on behavior (e.g. C-starts) could be expected over substantial ranges. Acoustic data transmission devices have been documented to elicit avoidance responses in captive odontocetes and pinnipeds at relatively low received levels. When extrapolating from captive experiments to wild animals, predicted impact zones would be large, possibly extending over several kilometers. However, further research is needed and these devices should not be implemented in areas of important habitat for pinnipeds or cetaceans. High-frequency or ultrasonic fish deterrents have the potential to influence behavior of odontocetes in a similar way as AHDs. However, no research into this has been carried out to date. The current scarcity of data makes it difficult to predict impact of any of the noise sources on invertebrates or other non-mammalian animals.

 

With respect to masking, particularly broadband high source level noise sources may constitute a problem (e.g. data transmission devices, AHDs). AHDs and data transmission devices (acoustic modems) could potentially mask the communication signals of delphinids. Lower-frequency sound sources (e.g. ocean research studies, tidal) may cause masking of communication signals in fish or pinnipeds. Tidal turbines may mask communication signals for a variety of species in the vicinity of the device due to the broad frequency spectrum of the noise emission. This may be particularly evident for fish which do not have sophisticated strategies to counteract masking like some marine mammals.

 

Hearing damage may only be caused by some of the high intensity noise sources mentioned in this chapter in species with good hearing sensitivity. Depending on the assumptions made, predicted impact zones may vary markedly. Odontocetes exposed to a single emission of an AHD are unlikely to suffer hearing damage even when being close to the device. However, repeated exposure for extended amount of times (e.g. as a result of overlapping sound fields from different devices) may pose a substantial risk. Similarly, long-term exposure to some data transmission devices may pose a risk that needs to be taken into account. Impact of the low-frequency sound sources (e.g. ocean tomography) on baleen whales and fish may be limited to the vicinity of the device. However, particularly with respect to fish, the possibility of strong inter-species variation needs to be considered and more data is needed. Since no direct measurements of hearing damage or even hearing abilities in baleen whales are available the possibility of underestimating the risk should also be taken into account.

 

In conclusion several noise sources described in this chapter have the potential to impact aquatic life. Although general conclusions can be drawn from the available data, knowledge gaps in certain areas will inevitably mean that some predictions have to be based on assumptions that might be potentially controversial. Therefore, it will be important to consider impact for many of the aforementioned noise sources on a case by case basis taking species, habitat and density of noise producers into account. However, mitigation measures should be implemented wherever possible.

Related Publications: 

Götz, T.; Hastie, G.; Hatch, L.; Raustein, O.; Southall, B.; Tasker, M.; Thomsen, F.; Campbell, J.; Fredheim, B. (2009). Overview Of The Impacts Of Anthropogenic Underwater Sound In The Marine Environment. Paper Presented at the OSPAR Convention. https://tethys.pnnl.gov/publications/overview-impacts-anthropogenic-underwater-sound-marine-environment

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