Underwater noise from maritime sourcesand

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

Vision can perceive many signals together in a space(overview)

Acoustic sense can perceive one signal at a time;the stronger one is heard

Acoustic signals from the environment for animal 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

Human activities that generate sound

• Shipping

• Fisheries– Benthic trawling– Sonar

• Mineral extraction

• Military activities – Sonar– Shooting / explosions

• Dredging

• Construction work

• Sequestration of carbon dioxide

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

Echolocation: fish detectionEcholocation: fish detection

distance >>

Background (sea) noise

So

un

d l

eve

l >

>

Loss at

reflection

Transmission loss of sound due to distance

Here the echo disappears in the sea noise

Echolocation click

echo

The level of background noise influences the potential of detection

Verboom, 2006

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

Examples of fish and marine mammal audiograms

Audiogram

30

50

70

90

110

130

150

170

4 8 16 31 63 125

250

500

1k 2k 4k 8k 16k

31k

63k

125k

Freq.

SP

L 1

Hz

ban

dw

idth

- d

B r

e 1

mic

roP

a

cod

seal

porpoise

herring

Hearing filters

-120

-100

-80

-60

-40

-20

0

4 8

16

31

63

12

5

25

0

50

0

1k

2k

4k

8k

16

k

31

k

63

k

12

5k

Freq.

dB

cod

seal

porpoise

herring

Audiogram:

Porpoise = guideline Verboom

Seal = guideline Verboom

Cod = Chapman & Hawkins (1973), Hawkins (1993)

Herring = estimate Enger (1967)

< resulting auditory filters

Verboom, 2006

Man-made sound and animal acoustic perception Weighted levels of pile driving noise

Red = Herring hearing spectrum Green = Porpoise hearing spectrum

Verboom, 2006

Animal perception of human-generated sound levelscalculated weighted source levels

Broadband (free-field) source level and weighted levels per species (dB re 1 microPa at 1 m)

  broadband cod h. seal porpoise herring

wind turbine pile driving 256 228 225 207 237

Airgun – seismic exploration 225 220 184 161 224

LFAS – military sonar 218 0 213 185 207

shipping noise upper limit 199 193 179 173 197

wind turbine in operation 193 162 148 135 176

shipping noise lower limit 160 144 138 122 148

man-made sound sources and marine animal acoustic windows

Man-made noise - free-field source levels (dB re 1 microPa at 1 m)

50

70

90

110

130

150

170

190

210

230

250

270

4

6.3 10 16 25 40 63 100

160

250

400

630 1k

1.6k

2.5k 4k

6.3k 10k

16k

25k

40k

63k

100k

160k

Frequency (Hz)

SP

L

(1

Hz

ban

dw

idth

)

harbour porpoise

harbour seal

large baleenwhale

cod

lobster

mollusc ???

1.5MW windturbine 193 dB

shipping upperlimit 199 dB

shipping lowerlimit 160 dB

pile driving(peak) 256 dB

airgun (example)225 dB

LFAS (example) 218 dB

Verboom, 2006

Dose-response relationship Porpoises

Radius of Shipping Noise for Porpoises is ~0 – 560 m, based on a Discomfort Threshold of 105 dB

Verboom, 2006

Avoidance of man-made sound hampered in crowded shipping areas

Shipping density = 45 Ships/Day

Netherlands Government, 1995

Migratory Routes(Shirihai & Jarett, 2006.Whales, Dolphins

and Seals)

Few migratoryroutes are known

Fish and invertebratesMigrate too

Grey Whale

Killer WhaleGlobal shipping densities as reported to AMVER (Source: AMVER 2002)

Evaluating the impact of man-made sound on marine life:

Frequencies and Sound Levels

- Frequency ->

Hearing properties

Irregular sound propagation

Masking of pure tone

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