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Underwater noise from maritime sources and impact on marine life

Underwater noise from maritime sources and impact on marine life. Cato C. ten Hallers-Tjabbes. Perceiving stimuli (signals) from the environment is vital for animal behaviour. In a marine environment vision is limited Acoustic sense and chemoreception instead.

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Underwater noise from maritime sources and impact on marine life

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  1. Underwaternoisefrom maritime sourcesandimpact on marine life Cato C. ten Hallers-Tjabbes

  2. Perceiving stimuli (signals) from the environment is vital for animal behaviour In a marine environment vision is limited Acoustic sense and chemoreception instead Vision can perceive many signals together in a space (overview) Acoustic sense can perceive one signal at a time; the stronger one is heard

  3. Acoustic signals from the environment foranimal behaviour and communication • Sounds generated in the physical environment: • Sounds from conspecifics: • Sounds from other species: • Predator/prey • Symbionths • Echolocation: self-generated signals • Navigation / orientation

  4. Human activities that generate sound • Shipping • Fisheries • Benthic trawling • Sonar • Mineral extraction • Military activities • Sonar • Shooting / explosions • Dredging • Construction work • Sequestration of carbon dioxide

  5. Impact of man-made sound on marine life • Temporary or permanent threshold shift = Deafening • Damage to hearing and other vital organs: • Excess sound disturbs the natural diving pattern. • Lethal if severe • Avoidance of favourable areas for Feeding, Reproduction, Shelter, a.o. • Inhibition of sensory-mediated behaviour

  6. How do marine animals detect sound The level of background noise influences the potential of detection Verboom, 2006

  7. Man-made noise may affect animal acoustic perception when: • The frequency range of man-made noise overlaps with the animal’s acoustic perception window and • Man-made noise is louder than the sounds animals are naturally perceiving The acoustic window to the outside world also offers an opportunity to enter [or intrude] Verboom, 2006

  8. Examples of fish and marine mammal audiograms Audiogram: Porpoise = guideline Verboom Seal = guideline Verboom Cod = Chapman & Hawkins (1973), Hawkins (1993) Herring = estimate Enger (1967) < resulting auditory filters Verboom, 2006

  9. Man-made sound and animal acoustic perception Weighted levels of pile driving noise Verboom, 2006 Red = Herring hearing spectrumGreen = Porpoise hearing spectrum

  10. Animal perception of human-generated sound levelscalculated weighted source levels

  11. man-made sound sources andmarine animal acoustic windows Verboom, 2006

  12. Dose-response relationship Porpoises Verboom, 2006 Radius of Shipping Noise for Porpoises is ~0 – 560 m, based on a Discomfort Threshold of 105 dB

  13. Shipping density = 45 Ships/Day Avoidance of man-made sound hampered in crowded shipping areas Netherlands Government, 1995

  14. Grey Whale Killer Whale Migratory Routes (Shirihai & Jarett, 2006. Whales, Dolphins and Seals) Few migratory routes are known Fish and invertebrates Migrate too Global shipping densities as reported to AMVER (Source: AMVER 2002)

  15. Evaluating the impact of man-made sound on marine life: Frequencies and Sound Levels Hearing properties Masking of pure tone Irregular sound propagation - Frequency ->

  16. Conclusions • Shipping and other man-made sound sources in the ocean are likely to increase • Shipping routes coincide with migratory routes of marine animals • The role of acoustic impact on ecosystem functioning may be much larger than currently understood • Sound levels of ships may be higher than necessary due to imperfectly moving mechanical parts, • Improving mechanical performance reduces excess sound levels and reduces operational costs • IMO may be the appropriate International Organisation to take a lead in developing a strategy to reduce the impact of man-made sound in the marine environment

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