Acoustic Effects of Tidal Energy

Status

Completed

Principle Investigator Contact Information

Name: Brian Polagye

Address: Box 3532600

Phone: +1 206 543 7544

Description

The purpose of this project is to better understand the acoustic effects of tidal energy devices through evaluation of the baseline environment (by prototyping several types of bottom-mounted and shore-based instrumentation), evaluating the implications of turbine noise at the site of a proposed pilot project in the context of existing ambient noise, using information from baseline monitoring to evaluate marine mammal behavior and responsiveness to existing sources of noise, and evaluate the effects that turbine noise could have on aquatic species through laboratory studies.

Funding Source

Subcontract through Snohomish Public Utility District via US Department of Energy competitive solicitation (2009).

Location of Research

Admiralty Inlet, Puget Sound, Washington.

Key Findings

Baseline Data Collection (UW):

Bottom-mounted packages may be used to simultaneously deploy Doppler profilers and passive acoustic hydrophones (though some caution is warranted to prevent interference).
Bottom-mounted packages may be used to characterize ambient noise in high-energy environments, provided that measurements are stratified to avoid contamination by flow noise.
Shore-based AIS systems are effective at quantifying vessel traffic and, when paired with long-term hydrophone data, can be used to quantify the contribution of vessel traffic to the ambient noise budget.
Shore-based infrared cameras can be extend the periods in which observations can be conducted (night, light fog), but have insufficient resolution to detect and identify marine mammals further than a few hundred meters from shore, while maintaining a reasonably broad field of view.

Turbine Noise in the Ambient Context (UW):

The noise that would be generated by operating turbines has a considerable overlap with existing anthropogenic noise sources at this site. Any post-installation noise characterization or observations of marine mammal responsiveness to turbine noise must acknowledge this and employ careful study design to avoid confusing turbine noise (or effects thereof) with other sources of noise or stimuli.

Marine Mammal Behavior (UW and SMRU, Ltd.):

Harbor porpoise are more commonly present at this site than at other proposed tidal energy developments. Generalized Linear Models suggest that echolocation activity is correlated with the time of day (many more clicks at night), current velocity (fewer clicks during periods of strong currents), ambient noise levels (fewer clicks during periods of elevated ambient noise), and stage of the tide (fewer clicks during spring than neap). However, such models have a large residual deviance, suggesting that, while these factors are statistically significant, they do not explain the majority of porpoise presence/absence at the site.
The local population of harbor porpoise may be habituated to periodically elevated noise due to omnipresent shipping and ferry traffic. Consequently, harbor porpoise at this location may not be responsive to turbine noise.

Laboratory Study (PNNL):

Juvenile Chinook salmon exposed to high intensity turbine noise continuously for 24 h developed minor and biologically insignificant injuries. Since turbine noise will be cyclic with the tide any effects of actual turbine noise are likely to be more subtle and not result in harm to juvenile or adult salmon.