Greening Blue Energy - BioTools For Business

7.8 Noise and avoidance by sea turtles
The hearing range of sea turtles is confined to low
frequent sounds (below 1kW, highest sensitivity
between 200 and 700 Hz, Ridgeway et al. 1969,
Bartol et al. 1999), which coincides with the frequencies
at which most noise occurs during operation
of wind farms. Experiments have shown that
low frequency sounds (25-750 Hz, 1.5-120 dB) can
cause startle responses, as well change in swimming
patters and orientation, among sea turtles (i.e. loggerhead
sea turtle Caretta caretta, O´Hara & Wilcox
1990, and see Samuel et al. 2005 for references).
Although, little is known on how these results translate
to impacts on the biology and ecology of sea
turtles (Samuel et al. 2005). It is worth noting that
sea turtles remain, forage and reproduce in coastal
areas with ambient sounds levels similar to those
around wind farms (Samuel et al. 2005). However,
sea turtles have strong fidelity to their foraging and
nesting areas, and to their migratory routes, and
may be inflexible in seeking alternative locations
when these are disturbed or blocked (Morreale et
al. 1996, Avens et al. 2003).
Conclusions
Broad-scale displacement of sea turtles is likely in
the short term during construction activities, but
out of the reproduction seasons overall impacts on
subpopulations/assemblages should be relatively
small. The displacement could, however, overlap
with periods for beaching and egg laying, hatching
and nursery periods, which could affect reproduc-
tion success. Certainty: 2
It is not likely that sea turtles would avoid the wind
farms during operation, considering their presence
in other urbanised areas. If avoidance would occur,
it should be very local , and impacts would thus
be small. If they would avoid larger areas, on the
other hand, there could be serious consequences
if construction takes place in or seaward to areas
important for reproduction. No (or very few) studies
or estimations regarding impacts on sea turtles
of offshore wind power development have been
conducted. Although relevant literature is scarce,
parallels can be drawn from some solid studies on
impacts of other activities. Certainty: 2.
7.9 Masking of ambient sounds and
bioacoustics
A wide range of marine species including mammals,
fish and crustaceans use sound to find their
prey, to communicate with each other (which often
linked to reproduction), to avoid predators and to
navigate (see e.g. Richardson et al. 1995, Wahlberg
& Westerberg 2005). The operational noise from
wind turbines is not considered sufficient to mask
communication of seals and porpoises (Madsen et
al. 2006, Tougaard et al. 2009). For fish however,
it is not known whether wind farms could mask
bioacoustics, and the implications this could have
on their ecological fitness and reproduction is not
known (Amoser & Ladich 2005, Wahlberg & Westerberg
2005). Low frequency sounds from the tur-
52 GREENING BLUE ENERGY - Identifying and managing biodiversity risks and opportunities of offshore renewable energy
bines may, for example, overlap with the mating
calls of gadoids (i.e. cod and haddock) with potential
consequences for community dynamics (Wahlberg
& Westerberg 2005).
Conclusions
Impacts on fish and mammal assemblages as a
whole of eventual local masking of bioacoustics
should, although long-term, generally be small.
There may be exceptions for isolated spawning
populations if a fish species is particularly sensitive
to this kind of disturbance. Little research is available,
though, and no studies have estimated what
long-term consequences any impacts could have.
Certainty: 2.
Impacts of sound disturbance from wind farms
on long distance communication and navigation
among mammals, such as whales during migration,
is largely unknown (Certainty 2). If likely at all,
impact on assemblages of porpoises, dolphins and
seals may generally be small, with special caution
for whales migrating long distances.
8 Electromagnetic fields (EMF)
The electricity generated by an offshore wind farm
is transmitted to the onshore network through 50
Hz (EU) and 60 Hz (USA) high voltage alternating current
(AC) or direct current (DC) cables. These cables
will emit EMF (electromagnetic field or electric and
magnetic fields). The electric field generated by the