L4 : Human noise in the Sea Flashcards

1
Q

why is sound important in the sea

A

sound travel 5x faster underwater
- light penetrates only shallow depths
thus sound being main sense for marine organisms

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2
Q

sound basics

A
  • pressure wave
  • measured in frequency (long wavelength = low freq.)
  • lower frequencies travel much further than high frequencies
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3
Q

sound propagation in the sea

A

speed of sound increases with the increasing water temp, increasing salinity and increasing density

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4
Q

Deep sound channel

A
  • sound waves in this layer get ‘trapped’ between water layers
  • near bermuda, at 1000m
  • shallower in temperate waters
  • beyond about 60 N or S it reaches the surface
  • sound can travel over 1000km
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5
Q

natural noise

A
  • earthquakes
  • ice
  • turbulance
  • breaking waves
  • rain
  • bubbles and spray
  • marine life…
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6
Q

shipping
[anthropgenic noise]

A
  • propeller cavitation, flow noise, engine noise
  • contributes noise 95-500 Hz (low freq)
  • increased low freq. noise to the ocean at a rate of 3d.b per decade (doubling every decade)
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7
Q

Seismic Surveys
[anthropgenic noise]

A
  • airgun : sends high energy sound into the seabed to find oil, determine seabed etc
  • sound concentrated <300 Hz but energy spills into higher frequencies (up to 15 kHz recorded)
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8
Q

Naval Sonar
[anthropgenic noise]

A
  • use high energy mid/low freq. sonar to find subs
  • low freq (LFA) = 100-500 Hz
  • mid freq. (MFA) = 2-8 kHz
    linked to whale strading and the bends
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9
Q

Construction
[anthropgenic noise]

A
  • detonations
  • pile driving
    a. offshore wind farm construction
    b. very loud noise
    c. 100 Hz - 10 kHz
  • temp. displacement of marine mammals
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10
Q

fisheries
[anthropgenic noise]

A
  • sonar to find fish
  • acoustic deterrents/pingers to scare marine mammals from nets
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11
Q

Science
[anthropgenic noise]

A
  • side scan sonar
  • fisheries sonar
  • ADCP (high freq. sound to measure ocean currents)
  • depth sounders
  • ATOC
  • play back experiments
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12
Q

ADCP

A

acoustic doppler current profiler

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13
Q

ATOC

A

acoustic thermometry of the oceans climate

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14
Q

Noise Legislation

A
  • noise classed as pollution under MSFD
  • guidelines on shipping noise under IMO
  • many species protected under various laws prohibiting harm or injury to protected species
  • monitoring & mitigation often required under EIAs
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15
Q

IMO

A

international maritime organisation

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16
Q

EIAs

A

environmental impact assessments

17
Q

UK noise monitoring networks

A

monitor baseline levels of noise
- determine good environmental status for noise pollution
- now includes Bangor and Plymouth

18
Q

GES

A

good environmental status

19
Q

Marine organisms and sound

A

most marine mammals use sound
- mammals have widest range of hearing
- seabirds and fishes also have good hearing in lower range (<4kHz)
- Human noise overlaps all species sounds from fish to marine mammals

20
Q

Cormorants sound

A

(bird)
- can hear sounds underwater between 1-4 kHz
the same freq. their prey - sculpin and herring vocalise at

21
Q

invertebrates sound

A

oysters can ‘hear’ the sounds of the sea
close at sounds between 10 Hz - 1 kHz

22
Q

TTS

A

-temporary threshold shift

23
Q

PTS

A

permanent threshold shift

24
Q

hearing

A
  • most known about odontocetes (toothed whales)
  • high freq. limit
  • maximum sensitivity
  • odontocetes sensitive to higher freq.
  • sensitivity overlaps vocalisation range
25
Q

difficulties measuring hearing sensitivity

A
  • requires captive animals
    limits species you can study
  • cant stimulate depth
26
Q

Death by noise

A
  • > 100 melon-headed whales died in 2008 NW Madagascar
    now linked to 12 kHz side-scan sonar for mapping of sea bed
    used by oil/gas research
27
Q

PTS / TTS : pile driving noise

A

PTS within 5m (cetaceans) and 20m (pinniped)
TTS within 10m (cetaceans) and 40m (pinniped)

28
Q

Increased stress / change in fitness

A
  • evidence for increased stress in right-whales from shipping traffic
  • noise reduced growth and reproduction rates brown shrimp
  • increased fish metabolic rate and predation with noise
29
Q

change in behaviour

A
  • displacement (move away from sound)
  • change in movement
  • change in vocalisations
  • change in surfacing patterns
    (- fitness consequences )
30
Q

grey seal pups and shipping noise
[case study]

A
  1. propagation models built
  2. feed model with true ship location (from AIS)
  3. overlay seal locations and dives - what noise do they hear?
31
Q

AIS

A

automatic identification system

32
Q

masking

A
  • when noise interferes with organisms ability to hear
  • masking navigation sounds (e.g evidence that reef fish find their reef from its sound)
33
Q

PCOD

A

population consequences of disturbance

34
Q

mitigation

A
  • ‘ramp-up’ of sound levels
  • MMOs on naval and seismic vessels (stop when animal seen/heard)
  • acoustic deterrents
  • avoidance to critical times/locations to animals
  • monitoring
35
Q

MMOs

A

marine mammal observers