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Federal Register / Vol. 86, No. 195 / Wednesday, October 13, 2021 / Proposed Rules
responses, autonomic nervous system responses, neuroendocrine responses, or immune responses e.g., Seyle 1950;
Moberg 2000. In many cases, an animals first and sometimes most economical in terms of energetic costs response is behavioral avoidance of the potential stressor. Autonomic nervous system responses to stress typically involve changes in heart rate, blood pressure, and gastrointestinal activity.
These responses have a relatively short duration and may or may not have a significant long-term effect on an animals fitness.
Neuroendocrine stress responses often involve the hypothalamus-pituitaryadrenal system. Virtually all neuroendocrine functions that are affected by stressincluding immune competence, reproduction, metabolism, and behaviorare regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction, altered metabolism, reduced immune competence, and behavioral disturbance e.g., Moberg 1987; Blecha 2000.
Increases in the circulation of glucocorticoids are also equated with stress Romano et al. 2004.
The primary distinction between stress which is adaptive and does not normally place an animal at risk and distress is the cost of the response.
During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated.
In such circumstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This is a state of distress, and it will last until the animal replenishes its energetic reserves sufficient to restore normal function.
Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well studied through controlled experiments and for both laboratory and free-ranging animals e.g., Holberton et al. 1996; Hood et al.
1998; Jessop et al. 2003; Krausman et al.
2004; Lankford et al. 2005. Stress responses due to exposure to anthropogenic sounds or other stressors and their effects on marine mammals have also been reviewed Fair and Becker 2000; Romano et al. 2002b and, more rarely, studied in wild populations e.g., Romano et al. 2002a. For example, Rolland et al. 2012 found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right
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whales. These and other studies lead to a reasonable expectation that some marine mammals will experience physiological stress responses upon exposure to acoustic stressors and that it is possible that some of these stress responses would be classified as distress. In addition, any animal experiencing TTS would likely also experience stress responses NRC, 2003, however distress is an unlikely result of this project, based on observations of marine mammals during previous, similar projects in the area.
MaskingSound can disrupt behavior through masking, or interfering with, an animals ability to detect, recognize, or discriminate between acoustic signals of interest e.g., those used for intraspecific communication and social interactions, prey detection, predator avoidance, navigation Richardson et al. 1995.
Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity, and may occur whether the sound is natural e.g., snapping shrimp, wind, waves, precipitation or anthropogenic e.g., pile driving, shipping, sonar, seismic exploration in origin. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest e.g., signal-tonoise ratio, temporal variability, direction, in relation to each other and to an animals hearing abilities e.g., sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age or TTS
hearing loss, and existing ambient noise and propagation conditions.
Masking of natural sounds can result when human activities produce high levels of background sound at frequencies important to marine mammals. Conversely, if the background level of underwater sound is high e.g., on a day with strong wind and high waves, an anthropogenic sound source would not be detectable as far away as would be possible under quieter conditions and would itself be masked.
Airborne Acoustic EffectsAlthough pinnipeds are known to haul out regularly in Narraganset Bay and some in the vicinity of the project area, we believe that incidents of take resulting solely from airborne sound are unlikely.
There is a possibility that an animal could surface in-water, but with head out, within the area in which airborne sound exceeds relevant thresholds and thereby be exposed to levels of airborne sound that NMFS associates with harassment, but any such occurrence would likely be accounted for in our
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estimation of incidental take from underwater sound. Therefore, authorization of incidental take resulting from airborne sound for pinnipeds is not warranted, and airborne sound is not discussed further here. Cetaceans are not expected to be exposed to airborne sounds that would result in harassment as defined under the MMPA.
Marine Mammal Habitat Effects The Navys construction activities could have localized, temporary impacts on marine mammal habitat by increasing in-water sound pressure levels and slightly decreasing water quality. Construction activities are of short duration and would likely have temporary impacts on marine mammal habitat through increases in underwater sound. Increased noise levels may affect acoustic habitat see masking discussion above and adversely affect marine mammal prey in the vicinity of the project area see discussion below.
During impact and vibratory pile driving, elevated levels of underwater noise would ensonify the project area where both fish and mammals may occur and could affect foraging success.
Additionally, marine mammals may avoid the area during construction, however, displacement due to noise is expected to be temporary and is not expected to result in long-term effects to the individuals or populations.
A temporary and localized increase in turbidity near the seafloor would occur in the immediate area surrounding the area where piles are installed. The sediments on the sea floor will be disturbed during pile driving; however, suspension will be brief and localized and is unlikely to measurably affect marine mammals or their prey in the area. In general, turbidity associated with pile installation is localized to about a 25-ft 7.6-m radius around the pile Everitt et al. 1980. Cetaceans are not expected to be close enough to the pile driving areas to experience effects of turbidity, and any pinnipeds could avoid localized areas of turbidity.
Therefore, we expect the impact from increased turbidity levels to be discountable to marine mammals and do not discuss it further.
In-Water Construction Effects on Potential Foraging Habitat The proposed activities would not result in permanent impacts to habitats used directly by marine mammals except for the actual footprint of the project. The total seafloor area affected by pile installation is a very small area compared to the vast foraging area
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