10 MARINE MAMMALS AND SEA TURTLES - Hebron Project

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Hebron Project Comprehensive Study Report Marine Mammals and Sea Turtles environmental effects on habitat use. The environmental effects of these activities on the marine mammal and sea turtle VEC in the Offshore Study Area are reviewed in Section 10.5.1.3 (Habitat Use). 10.5.1.3 Change in Habitat Use This effect category includes behavioural effects of project activities on marine mammals and sea turtles. Noise introduced into the water column has the greatest potential to impact the behaviour of marine mammals and sea turtles, as noise is associated with almost every aspect of the construction, operations and maintenance, and decommissioning and abandonment phases of the Project and this VEC is known to be sensitive to noise. Behavioural reactions of marine mammals (and sea turtles) to sound are difficult to predict in the absence of site- and context-specific data. Reactions to sound, if any, depend on species, state of maturity, experience, current activity, reproductive state, time of day, and many other factors (Richardson et al. 1995; Wartzok et al. 2004; Southall et al. 2007; Weilgart 2007). If a marine mammal reacts to an underwater sound by changing its behaviour or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant (e.g., Lusseau and Bejder 2007; Weilgart 2007). Nearshore Construction of the Bund Wall Pile driving produces impulsive sounds whose levels are high enough to cause behavioural effects in marine mammals and sea turtles which may result in a change in habitat use. Southall et al. (2007) suggest that for all sound types, other than single pulses (like those from an explosive), behavioural effects will occur more commonly at sound levels below those involved with TTS or PTS. Based on available literature, a 160 dB re 1 μPa (rms) disturbance criterion is suggested for pile driving activities. Results of acoustic modelling (JASCO 2010) indicate that received sound levels greater than 160 dB re 1 μPa (rms) do not typically extend beyond 3.1 km for pile driving activities in the Nearshore Study Area at both the bund wall and deepwater mooring site. Rather, it is predicted that 160 dB re 1 μPa (rms) levels will extend to 2.9 km and 3.1 km from the bund wall and deepwater mooring site, respectively. Indo-Pacific humpback dolphins (Sousa chinensis) that likely have similar hearing abilities as NW Atlantic delphinids occur in nearshore waters near Hong Kong, where in-water pile driving has been used extensively for building piers and other structures (Jefferson et al. 2009). A study indicated that some Indo-Pacific humpback dolphins exposed to sound pressure levels of 170 dB re 1 µPa (rms) remain within 300 to 500 m of the pile driving area before, during, and after operations (Würsig et al. 2000). Although some dolphins temporarily abandoned the work area, their numbers returned to close to 10-48 June 2010
Hebron Project Comprehensive Study Report Marine Mammals and Sea Turtles those seen pre-construction during the follow-up survey seven months after construction activities ended (Würsig et al. 2000). Several studies monitored harbour porpoises during construction of two offshore wind farms off the coast of Denmark (Tougaard et al. 2003, 2009; Carstensen et al. 2006; Teilmann et al. 2008). During pile driving activities (using both vibratory and impact techniques) at the Nysted offshore wind farm, a significant decrease in echolocating activities and abundance was reported within the construction area and in a reference area 10 km from the construction site. Two years after construction, echolocation and presumably porpoise abundance were significantly reduced (Carstensen et al. 2006; Teilmann et al., 2008). During percussion pile driving at the Horns Reef wind farm, harbour porpoise acoustic activities declined, although the recovery to baseline occurred only hours after completion of these activities (Tougaard et al. 2003, 2009; Teilmann et al. 2008). Behavioural changes during the construction period included a decrease in feeding behaviour and a decrease in the number of individuals in the area (Tougaard et al. 2003). Ringed seals exposed to pile-driving pulses exhibited little or no reaction to impact pipe-driving sounds at a shallow water site in the Alaskan Beaufort Sea (Blackwell et al. 2004). At the closest point (63 m), received levels were 151 dB re: 1 µPa (rms) and 145 dB re: 1 µPa 2 -s SEL. Harbour seal haul-out behaviour was affected by pile-driving at an offshore wind farm (Nysted) in the western Baltic (Edrén et al. 2004). The authors found a 31 to 61 percent reduction during periods with pile driving vs. no pile driving in the number of seals hauled out at a beach approximately 10 km from the construction site. Sound levels were not measured and observations of seals in the water were not made. The authors suggest that seals may have spent more time in the water because this is a typical response to disturbance or the seals may have used an alternate haul-out site. At an adjacent wind farm to Nysted (Horns Rev), no seals were observed during ship-based surveys in the wind farm during pile driving. The reactions of harbour seals to the pile driving appeared short-term because aerial surveys did not reveal any decrease in overall abundance during the construction period (2002 to 2003) (or operation period 2004 to 2005; Teilmann et al. 2006). Based on this limited information and the literature for marine mammal response to low-frequency impulsive sounds (like airgun pulses - see Richardson et al. 1995 and Nowacek et al. 2007), baleen and toothed whales would likely exhibit at least localized avoidance of the pile driving sites. There is some evidence to suggest that harbor porpoise echolocation activity may decline, at least temporarily, and that seals may exhibit at least short-term avoidance of the area. There are currently no published data available for behavioural effects of pile driving on sea turtles. Of note, sea turtles are considered rare in inner Trinity Bay near the sites of potential pile driving. Mitigation measures associated with limiting effects to habitat quality were previously described (see Section 10.5.1.2) and will additionally minimize potential effects to habitat use by marine mammals and sea turtles. 10-49 June 2010
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10 MARINE MAMMALS AND SEA TURTLES - Hebron Project

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