BSEP116B Biodiversity in the Baltic Sea - Helcom

6.8 Noise pollution
Several anthropogenic activities produce underwater
noise pollution in the coastal and marine environment,
for instance ship and boat traffic, their
echo-sounders, seismic surveys, drilling, pile-driving,
SONARs, underwater explosions, extractions,
gas pipeline work and operation and wind farm
operations. Marine animals that rely on hearing are
at risk of being affected by underwater noise either
by interference with biological signals, exclusion
from natural habitats, stress, and even by direct
physical harm and tissue damage.
Information on ambient noise levels and their
actual impact on animals in the Baltic Sea area are
largely missing. This section gives an overview of
noise generation from activities that are present
in the Baltic Sea and the known sensitivity of
mammals and fish to noise in their habitat.
6.8.1 Hearing in the marine
environment
The impact of noise depends on the intensity level
(loudness) and frequency, the duration as well
as the frequency of repetition of the sound, the
transmission loss from a source to the animal, and
the hearing sensitivity of the animal. An animal can
detect the sound when the frequency of the source
overlaps with the animal’s frequency window for
hearing, and if the noise is more intense than the
animal’s threshold level for hearing. Figure 6.8.1
shows the hearing threshold levels for harbour porpoise
(Phocoena phocoena), harbour seal (Phoca
vitulina), and selected fish species as well as the
intensity levels of some common anthropogenic
activities in the Baltic Sea.
When anthropogenic noise has frequencies similar
to biological signals, the noise may interfere with
signals used for communication and location, an
effect that is called masking. Known behavioral
changes of mammals in response to noise include
changing surfacing and breathing patters, changing
their communication frequencies, disruption
of social connections, stress etc. and may result in
active avoidance of areas with high sound levels and
also greatly reduce the distance over which communication
is possible. In the immediate vicinity of
some anthropogenic activities such as using airguns
and certain SONARs, the noise can be loud enough
to cause immediate and permanent hearing damage
to both mammals and fish. For a more complete list
of impacts on and responses of cetaceans to anthropogenic
noise, see Nowacek et al. (2007).
Treshold level for hearing at frequency of
best hearing, given in table
Intensity level of activity at frequency of
intense noise, given in table
At frequency
(kHz)
Frequency range
of hearing/activity
(kHz)
Salmon
Herring
Cod
Harbor seal
Harbor porpoise
Explosives (1 lb. TNT)
Low power acoustic deterrent device
Fish finder/echosounder
Air-guns (seismic industry)
Wind fram operation
Pile-driving
Fishing vessel
Large tanker
0.16 0.03 - 1
0.1 0.03 - 1
0.16 0.03 - 1
8-16 0.1 -100
16-140 0.25 -140
1 Broad-band
2.5 - 10 2.5 - 160
50/200
0.05 -0.3 0.01 -3
0.125 0.01 - 0.5
0.2 0.02 - 20
0.1 0.02 - 10
0.1 0.02 - 10
0 50 100 150 200 250 300
Intensity (dB)
Figure 6.8.1. Hearing sensitivity of marine animals (red) in the Baltic Sea and intensity levels of common
activities (blue). Intensity levels for all activities are given at a reference pressure of 1µPa. The information
stems from specific systems and models. Variations occur. Sources: NRC 2003, Thomsen et al. 2006 and references
therein.
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