Document ID: chunk:federal_register_of_legislation:F2015L01633:body:0:p25
Version: federal_register_of_legislation:F2015L01633
Segment Type: other
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Character Range: 68102–71109

pH of sea water33. Laboratory experiments have shown that ocean acidification can be detrimental to Antarctic krill embryo development58, which would consequently affect krill predators such as blue whales.

5C Noise Interference
Anthropogenic underwater noise covers a large range of frequencies, and the way in which a species is impacted by these sounds will depend on the proximity to the source, hearing sensitivity of the whale, intensity of source and its frequency spectrum, and the behavioural state of the whale49,84,104. The effects of elevated noise levels on marine mammals is known to include: avoidance of an area, tissue rupture, hearing loss, disruption of echolocation, masking (the inability of a whale to detect sounds important to it), habitat abandonment, aggression, calf abandonment, and behavioural disturbance. It is the high intensity signals with high peak pressures received at very short range that can cause acute impacts such as injury and death. The impact of anthropogenic noise that is received further away from the source but that occurs continuously can include hearing impairment (e.g. permanent and temporary threshold shifts) masking of communication, displacement, and other significant behavioural changes (including to vocal behaviour).
The purpose of different vocalisations in baleen whales, including blue whales, is still uncertain. It is difficult to link individual callers with their sex and behaviours to determine the role of specific calls, though suggested purposes include foraging, communication and association with breeding activities86.
Blue whales produce powerful (188 dB re: 1 µPa @ 1 m), low frequency (10-500 Hz) sounds compared to other animals, including other cetaceans29, 74. They also have relatively stable call characteristics over time76. They have experienced a decrease in their tonal frequency globally over years but the reasons for this are currently unknown41,75. Sound travels faster through water than air and low frequencies are able to travel further than high frequencies. Therefore blue whales are able to communicate over hundreds of kilometres in some environments107. Blue whale calls vary across geographic regions76, and within at least the eastern North Pacific it has been shown that call types vary depending on the caller's sex, behaviour and pod size86, 87.
There has been no blue whale audiogram produced to indicate their hearing range and sensitivity at different frequencies. This is largely because such characteristics are difficult to measure in cetacean species not kept in captivity. However, ear morphology in Mysticetes (baleen whales) show they are specialised for hearing low frequencies compared to Odontocetes (toothed whales), and that they are likely capable of hearing outside their vocal range60. Given this lack of defined sensitivity for blue whales it is difficult to accurately assess whether a particular type of man-made sound would affect blue whales.
Masking by anthropogenic noise can