BSEP116B Biodiversity in the Baltic Sea - Helcom

6.8.2 Activities generating noise in
the Baltic Sea
Industrial activities
Industrial noise frequently originates from few,
more or less stationary sound sources during
resource exploration, extraction, construction and
operation of wind turbines as well as use of deterrent
devices in fisheries such as pingers.
During pile-driving operations associated with
construction, e.g. of wind farms, noise is produced
at high intensity levels at broad-band frequencies.
Pile-driving is estimated to be audible for harbour
porpoises and harbour seals at least 80 km from
the source (Thomsen et al. 2006) Within this zone
the noise can potentially interfere with communication
and echolocation clicks. The zone where
behavioral changes can be expected range from
a few up to 20 km, and hearing loss may occur
within a few hundred meters up to a few kilometers
from the pile-driving. Hearing capability
differs considerably between fish species (Figure
6.8.1). For cod and herring that have relatively
good hearing the audible zone is estimated at up
to 80 km and behavioral changes are considered
possible close to the pile-driving activity (Thomsen
et al. 2006).
Underwater explosion
Operational noise of wind turbines is of lower
intensity than pile-driving and the impact on both
mammals and fish is likely to be restricted (Madsen
2006). However, noise simulations show that even
operating turbines may have a potentially masking
effect at least at short ranges in the open sea
(Lucke et al. 2007). Direct studies on the response
of mammals to operating wind farms are currently
taking place in the Danish wind farm “Nysted”
(Diederichs et al. 2008, Teilmann et al. 2008).
High pressure airguns are commonly used in
seismic surveys to produce sound pulses of low
frequency and high intensity. There are several
observations of behavioral change of mammals
associated to airgun operation, in particular involving
avoidance of the area surveyed (Gordon et al.
2003) as well as ceased communication and physical
effects on cetaceans (Nowacek et al. 2007).
In the immediate vicinity of airgun operation fish
kills have been observed. Reduced catches of fish,
e.g. cod, have also been noted in areas of seismic
surveys, lasting up to several days after the activity
has ceased (Engås et al. 1996).
Industrial seismic surveys use large arrays with multiple
airguns to locate geological structures associated
with oil and gas. Airguns are also used in geological
mapping in the Baltic Sea area, usually involving
fewer airguns with lower impact than those used
for exploration surveys. However, all air guns can be
heard over very long distances under water.
High-frequency SONARs (>10 kHz) that are commonly
used to map the seafloor or to locate fish
are within the hearing frequency of many marine
mammals, but they have a limited transmission
range in water. Masking effects cannot be disregarded
although concrete evidence is still lacking.
Recent research (M. Lahtinen, pers. comm.) indicates
that depth and fishing echo-sounders using
50 kHz frequency can be problematic for toothed
whales and possibly seals, as this frequency is in
their important hearing range. Even small boats and
fishing vessels have these echo-sounders on almost
continually whenever map plotters are being used.
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Ship traffic
Shipping constitutes a rather diffuse and omnipresent
sound source that is difficult to quantify
and evaluate. However, large cargo vessels