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For instance, the extent and type of colonisation
of turbines will depend on the proximity and connectivity
(including current patterns) to existing
hard habitats that could supply larvae and propagules
(Cummins 1994, Svane & Petersen 2001). The
diversity of shallow water fishes associated with the
turbines is also likely to decrease with distance from
the shore (e.g. Molles 1978, Gladfelther et al. 1980,
Cummins 1994). With increasing exposure to wave
action, delivery of rates of plankton to the turbine
habitats is likely to increase, benefiting filter feeding
animals such as mussels and planktivorous feeding
fish (Wilhelmsson et al. 2006).
Depth is a key structuring factor in the marine environment
(e.g. Pedersén & Snoeijs 2001, Ponti et al.
2002). Littoral species, particularly on rocky shores,
as well as subtidal species are typically confined to
specific depths defined by the physical and biological
characteristics of the habitat, such as light and
wave conditions, temperature, and competition for
space and other resources (Gibson 1969, Bohnsack
et al. 1991). In particular for transient fish species,
the depth at which turbines are situated may be
the most important factor for the magnitude of fish
aggregation effects (Moffit et al. 1989). Salinity also
affects the assemblages present in the area (e.g.
Mann 1991). Latitudinal, regional, and local factors,
thus, influence species, habitats and their sensitivity
to wind farm development. In addition, acceptable
levels of disturbances will depend on the local/
regional conservation status of the species or habitats
in question.
13 Conclusions
To date, wind farm related research and monitoring,
along with related research, indicates that the
largest potential impacts of offshore wind power
development take place during the construction
phase. Disturbance from noise and seabed disruption
during the construction phase could lead
to loss of feeding, spawning and nursing grounds
for e.g. fish, marine mammals, and birds for varying
periods of time, and could also adversely affect
sensitive benthic species and habitats. Although
impacts often seem to be short-term or spatially
limited, the acceptable levels of disturbance will
ultimately depend on the local/regional conservation
status and sensitivity of the species or habitat
in question.
On the other hand, if offshore wind power development
is well planned and co-ordinated the local
subsurface marine environment could even benefit
from wind farms in several aspects. (e.g. trawling
exclusion and habitat enhancement for many species).
Knowledge on the various disturbance effects on
the marine environment for offshore wind power
is increasingly substantiated due to the realisation
of several long-term monitoring programmes along
with targeted studies and experiments. However,
most programmes were only recently initiated and
many research contributions are limited to method
development. Additionally, the majority of studies
and experiments are limited to single species sys-
tems, and there is little elaboration at ecosystem
scale. Furthermore, Environmental Impact Assessments
do not regularly address additive environmental
effects of existing activities or other planned
developments, including strategic aims for offshore
wind power. To improve this, criteria and methods
for assessing cumulative effects need to be
designed and standardised at appropriate temporal
and spatial scales
Through continued and enhanced monitoring of
carefully selected environmental (biotic and abiotic)
and species-specific parameters during construction
and operation of offshore energy farms,
adverse and positive impacts could more reliably
be recognised. This would facilitate the process of
identifying and achieve concurrence on areas to
be considered for offshore wind power, as well as
advance the development of methods and mitigating
measures for the benefit of the marine environment.
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