Marine Mammals, Noise and Tidal Turbine Demonstration Sites

The potential impacts of collision, habitat alteration and anthropogenic noise on marine mammals remains a concern for any large-scale renewable energy development using tidal in-stream turbines. Turbines are considered to emit regular periods of ‘continuous’ noise, at frequencies and levels that are both detectable to most marine mammals and may cause behavioral disturbance. Porpoises favor high energy sites and are known to respond adversely to construction noise, but their response (plus those of dolphins and seals) to the noise emitted from turbines is largely unknown. Assessing the potential for exclusion or blocking effects is considered vital for future turbine developments.

We review current information from three different studies, the ongoing Before-After-Impact studies at the Marine Current Turbine (MCT) SeaGen site operating in Strangford Lough (Northern Ireland), impact studies at the Fundy Ocean Research Center for Energy’s demonstration site in Minas Passage (Bay of Fundy, Nova Scotia), where Nova Scotia Power Inc. deployed one (non grid-connected) OpenHydro tidal turbine device and baseline studies at Snohomish PUD’s proposed demonstration test site in Admiralty Inlet (Washington State, USA). Data from the MCT site includes information on harbor porpoise using POD hydrophones (an autonomous cetacean echolocation click detector) deployed in a gradient study design over three years, in addition to telemetry data from 36 harbor seals, deployed with SMRU GPS tags before construction, during construction and during turbine operations and land-based observer data. Data from the Bay of Fundy includes a POD monitoring study (with PODs deployed near-turbine and in a control site) and seasonal observer studies. POD data has also been collected in Admiralty Inlet for a two year baseline, in addition to observer and acoustic studies focusing more on Southern Resident killer whales and pinnipeds.

Results from these studies highlight the advantages (and limitations) of using passive acoustic monitoring techniques. They also highlight the scale of site-specific differences in marine mammal use and how this directly impacts present and future monitoring studies. We report on the present level to which porpoise and seal behavior changes due to the presence and operation of the MCT turbine and the extent to which the structural presence of a non-operating turbine may impact local porpoise use and behavior. Finally, we aim to summarize the available data and the future monitoring approaches planned (and needed) to fulfill even a basic understanding of the potential impacts of both noise from operating turbines and also their long-term structural presence.