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will be prohibited inside energy parks. This would
cause less physical disturbance of benthic communities
and more favourable environments for longlived
species (Dayton et al. 1995, Jennings & Kaiser
1998, Kaiser et al. 2006, Tillin et al. 2006).
Conclusions
Particularly on soft bottom habitats, but to some
extent also on hard bottom dominated areas, the
addition of hard substrata increases habitat heterogeneity
and the biodiversity of sessile organisms.
These long-term changes should be very local, and
limited to the turbines and the adjacent seabed.
The magnitude of these effects is not assessed here,
due to the fact that although the habitat alterations
will be localised to the turbines, total biomass of
species and diversity may increase notably for the
area as a whole. Research on fouling communities
on artificial and natural hard substrata is relatively
well advanced, and the bases for general predictions
are good, although variability among localities
and environmental conditions limits predictability.
Certainty: 4
In the long term, trawling exclusion enhances abundance
of several species fish within the whole wind
farm area (broad), and effects can be considered
large. Certainty: 5.
3.2. Dispersal patterns of hard bottom species
Wind turbines provide hard substrata in regions and
at depths often dominated by soft bottom habitats.
Wind farms could thus fill in gaps between natural
areas of hard substrata, and so change the biogeographic
distribution of species within a region (Bulleri
& Airoldi 2005, Nielsen 2009). Not only may
the distribution of native reef species be affected
by this. Based on studies on pier pilings and oil
platforms, it has been suggested that large scale
urbanisation of coastal areas could provide entry
points and stepping-stones for alien rocky shore
species brought in as larvae by ballast water (Glasby
& Connell 1999, Connell 2001, Airoldi et al. 2005,
Bulleri & Airoldi 2005, Page et al. 2006, Glasby et
al. 2007, Villareal 2007). Artificial structures have
also been shown to better cater for non-native species
than natural reefs by changing the competitive
interactions (Fenner & Banks 2004, Sammarco et
al. 2004, Bulleri & Airoldi 2005, Glasby et al. 2007).
Three non-indigenous species have been recorded
on wind turbines in Denmark and Sweden (Dong
Energy et al. 2006; Brodin and Andersson 2008).
Two of these species dominated their respective
sub-habitat. One of the species was also recorded
as an exotic species in large densities on offshore
oil platforms off California and concerns were raised
on how it may influence native amphipod species
(Page et al. 2006).
Conclusions
The significance of these effects would vary greatly
36 GREENING BLUE ENERGY - Identifying and managing biodiversity risks and opportunities of offshore renewable energy
among regions, depending on geography, hydrology,
existing artificial structures (e.g. buoys, pier pilings,
and coastal defence structures), seabed type,
and species compositions. As development of wind
farms progresses, effects on dispersal patterns of
certain species within a region may be significant.
The long-term effects on sessile species could be
very broad, but although there may be impacts, too
little information is available on overall impacts on
benthic assemblages to make firm predictions. The
influence of the structures on connectivity and dispersal
patterns of marine organisms has not been
established. Un-proportionally large assemblages
of non-indigenous species on artificial structures
are, nevertheless, relatively well documented.
Certainty: 2.
3.3. Fish and mammals
Construction and deployment of artificial reefs
in coastal waters is practiced worldwide with the
intent to manage fisheries, to protect and facilitate
the rehabilitation of certain habitats or water
bodies, or to increase the recreational value of an
area (Ambrose 1994, Brock 1994, Guillén et al. 1994,
Hueckel et al. 1989, Milon 1989, Pickering et al.
1998, Wilhelmsson et al. 1998, Jensen 2002, Claudet
& Pelletier 2004, Seaman 2007). The materials
used range from specially designed concrete- or
steel units to scrap materials such as car tires, shipwrecks,
and train carriages (Baine 2001). Although
some studies have revealed no significant effects
of artificial reefs on fish assemblages, accumulated