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Cetaceans, bioindicators of noise pollution: understanding the changes of the marine environment
ple some of the Exclusive Economic Zones around North
West Europe (see OSPAR 2009). Potential effects might
not be proportionate to pollution levels due to variation in
sound propagation and - most importantly - the distribution
of marine life that is sensitive to sound.
Acoustic bioindicators
Cetaceans are acoustic bio-indicators. Marine mammals,
notably cetaceans, depend on acoustic exchange for a great
number of activities and vital behaviors such as communi-
cation, geographical orientation, habitat use, feeding and
a wide range endeavors within the broader social group
(cohesive action, warnings and maternal relationships).
On account of their fundamental role in the balance of the
marine food chain, cetaceans are considered as indicators
of the interaction with anthropogenic noise.
A distinction must be made between “Sources of noise” and
“Acoustic signals”. The reason for this separation lies in the
following: human activities in the ocean can generate resi-
dual noise that is associated with that activity but does not
contain nor provide data. Shipping noise, oil and oceano-
graphic platform construction, wind turbines or seabed dril-
ling, for example, all fall into the category of “noise”; we are
dealing with activities that “might” function without noise if
they could rely on adequate available technology and prac-
tices. There are other activity groups which include military
and industrial sonar, seismic and geographical surveys that
are based on the usage of acoustic signals, i.e. sound sour-
ces introduced into the medium to extract information, and
whose substitution would be very difficult, at the moment,
to bring about. Lastly, we consider as acoustic signals the
biological sources produced by marine organisms.
In the past hundred years the scale of anthropogenic noise
introduced into the marine environment has grown to unpre-
cedented levels. There is no doubt that in recent history, the
larger oceangoing organisms, particularly cetaceans, have
not yet developed the ability to adapt their auditory capaci-
ties to these powerful sound sources, whose impact on the
functioning of their vital systems remains unknown.
The sources of marine noise pollution produced by human
activity, includes, amongst others, maritime transport, oil
and gas exploration and exploitation, industrial and mili-
tary sonar, experimental acoustic sources, undersea explo-
sions; military and civilian, engineering activities, super-
sonic aircraft noise and the construction and operation
of sea-based wind farms.
These sound sources invade the acoustic and physical
space of marine organisms (Figure 1) and there is no
actual field of reference in which to foresee the negative
consequences of these interactions on the ocean’s natu-
ral equilibrium, and their short, medium and long term
effects on marine biodiversity.
Even though land based environmental noise has been
regulated since some time, only recently has marine
acoustic pollution been introduced in legal international
frameworks1, becoming national regulations in countries
such as the United Kingdom.
Fig. 1 : Sound levels and frequencies from
anthropogenic and natural sound sources in the
marine environment (Boyd et al. 2008)
The Council of the European Cetacean Society, a society
of some 500 European scientists dedicated to cetacean
biology research, considers that 2 :
- There is an urgent need for research into the effects of
man-made acoustic pollution in the sea, research that
must be conducted under the highest standards of scien-
tific credibility, avoiding all conflicts of interest.
- Non-intrusive mitigation measures must be developed
and implemented as soon a possible.
- There will have to be a limitation put on the use of power-
ful underwater sound sources until the short, medium and
log term effects on marine mammals are known and the
use of such sources is avoided in areas where concentra-
tions of these animals are found.
- Legislative instruments must be developed with regard
to marine acoustic pollution that will permit compliance of
European and national policies on the protection of marine
biodiversity.
Still even more recently, the Convention on Migratory
Species (CMS), recognizing that…
… anthropogenic ocean noise constitutes a form of pollu-
tion which may degrade the marine environment and also
have adverse effects on ocean fauna, even resulting in indi-
vidual fatalities and reaffirming that the difficulty in deter-
mining the negative acoustic impact on cetaceans requi-
res the drawing up of precautionary principles in cases
where impact is possible,
…has just published among other resolutions3, one that urges
bodies whom exercise jurisdiction over any species of marine
organisms listed in the appendices of the CMS, to…
… develop methods of control on the impact of acous-
tic emissions arising from human activities in suscepti-
ble habitats that serve as gathering points or places of
passage of endangered species, and to carry out envi-
ronmental impact studies on the introduction of systems
that may produce noise and their derived risks to marine
mammal species.
1- These regulations include articles 192, 194 (2.3), 206 and 235 of UNCLOS
1982 and UNCED 1992.
2- Conclusions from the 17th International Conference held in Las Palmas, Canary
Islands in March 2003, under the main theme of Marine Mammals and Sound.
3- Ninth meeting of the parties, Rome 2008