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the whole wind farm area itself (Maar et al. 2009).
Conclusions
The long-term influences of potential up- or downwelling
at the perimeter of a wind farm may be
measurable in the area as a whole, although effects
on species or ecosystem functions should be local
and small. No field observations confirming the
model have yet been reported, and studies on
potential impacts on biota within wind farms are
scarce. Certainty: 1.
Changed hydrodynamics around turbines in operation
are likely to have long-term effects on the
nature of subtidal sediments and thus the assemblage
structure of benthic organisms, but those
will be local, limited to the surroundings of each
turbine. Altered water flows by artificial reefs and
other structures, and the influences on adjacent
seabeds are relatively well studied. Measurable
effects of altered transports of organic material and
nutrients, as well as increased predation on benthic
organisms, are long-term but should be local, i.e.
within a few meters up to 100 m from a turbine, and
very local for potential anoxic conditions. Careless
siting of turbines could, however, affect threatened
species with narrow distribution ranges, but overall,
the degree of severity of effects may on average
range between small and moderate. Accumulated
evidence from related research areas is comparably
strong, and a few studies have been conducted in
wind farms, but the dynamics of predation effects
are unclear. Certainty: 4.
6 Toxic substances
Antifouling paints to inhibit fouling are often used
on submerged structures. According to international
expertise (e.g. GESAMP), the only constituent chemicals
of significant danger in the marine environment
are mercury, tin and cadmium, primarily due
to their bioavailability, and potential to accumulate
in the food chain. These metals are reportedly not
released during construction and operation of wind
farms. Antifoulants typically release toxic chemicals,
but use is largely regulated towards licensed protective
coatings that are low- or non-toxic. For example
some wind turbines are painted with glass flake
reinforced polyester coatings with no biocide activity,
and antifoulants are typically not used.
Measurements of trace metals, volatile solids,
copper, zinc and hydrocarbons have shown no
anomalies in mussels, crabs and fish around oil
platforms in the California Bight (Schroeder & Love
2004). The risks of pollution from wind turbines
should be even lower. There is, however, a legacy of
our part history of contaminants in a many coastal
areas adjacent to industrial estuaries and coast.
The largest risks of negative environmental impacts
from pollution will most probably arise while dredging
sediments containing pollutants (Nendza 2002),
and although these effects are likely to be local and/
or temporary, caution is needed when constructing
many turbines over a longer time. In relation to a
specific offshore wind farm project the estimated
release of metals and organic substances would
lead to increased concentrations of less than 10%
44 GREENING BLUE ENERGY - Identifying and managing biodiversity risks and opportunities of offshore renewable energy
of background levels. It has, nevertheless, been
pointed out that copper contamination of filterfeeding
organisms on the seabed adjacent to the
turbines, as well as of plankton, may occur (DHI
1999, Bio/consult 2000b). Maintenance sandblasting
and painting could release several cubic meters
of paint and sand unless this is removed or excluded
from the water (Bio/consult 2000b). Further, when
changing oil in transformer stations, release of service-aged
oil needs to be avoided.
Conclusions
Serious pollution does not seem likely, and if pollution
would occur effects on biotic assemblages
should be local and overall effects thus small, provided
that there are no large oil spills when serving
transformer stations. The risk of stirring up polluted
seabeds and variability in construction methods
among developers bring in some uncertainty, but
research and information base is otherwise good.
Certainty: 4.
7 Acoustic disturbance
7.1 Construction noise and injuries on
vertebrates
There has been a dramatic increase in anthropogenic
underwater noise in coastal areas during the
last few decades (Samuel et al 2005, Tougaard et
al. 2009). Hearing and processing of sound differ