Summary
- The rapid increase in the number of tidal stream turbine arrays will create
novel and unprecedented levels of anthropogenic activity within habitats
characterized by horizontal current speeds exceeding 2ms-1
However, the potential impacts on pursuit-diving seabirds exploiting these tidal
stream environments remain largely unknown. Identifying similarities between the
fine-scale physical features (100s of metres) suitable for array installations, and
those associated with foraging pursuit-diving seabirds, could identify which
species are most vulnerable to either collisions with moving components, or
displacement from these installations.
- A combination of vessel-based observational surveys, Finite Volume
Community Ocean Model outputs and hydroacoustic seabed surveys provided
concurrent measures of foraging distributions and physical characteristics at a
fine temporal (15 min) and spatial (500 m) resolution across a tidal stream
environment suitable for array installations, during both breeding and non-breeding
seasons. These data sets were then used to test for associations between
foraging pursuit-diving seabirds (Atlantic puffins Fratercula arctica, black guillemots
Cepphus grylle, common guillemots Uria aalge, European shags Phalacrocorax
aristotelis) and physical features.
- These species were associated with areas of fast horizontal currents, slow
horizontal currents, high turbulence, downward vertical currents and also
hard-rough seabeds. The identity and strength of associations differed among
species, and also within species between seasons, indicative of interspecific and
intraspecific variations in habitat use. However, Atlantic puffins were associated
particularly strongly with areas of fast horizontal currents during breeding seasons,
and European shags with areas of rough-hard seabeds and downward vertical
currents during non-breeding seasons.
- Synthesis and applications. Atlantic puffins' strong association with fast
horizontal current speeds indicates that they are particularly likely to interact with
installations during breeding seasons. Any post-installation monitoring and
mitigation measures should therefore focus on this species and season. The
multi-species associations with high turbulence and downward vertical currents,
which often coincide with fast horizontal current speeds, also highlight useful
pre-installation mitigation measures via the omission of devices from these areas,
reducing the overall likelihood of interactions. Environmental impact assessments
(EIA) generally involve once-a-month surveys across 2-year periods. However, the
approaches used in this study show that more focussed surveys can greatly
benefit management strategies aiming to reduce the likelihood of negative
impacts by facilitating the development of targeted mitigation measures. It is
therefore recommended that these approaches contribute towards EIA within
development sites.
Keywords:
bathymetry,
Cepphus grylle,
foraging ecology,
Fratercula arctica,
FVCOM,
hydrodynamics,
Phalacrocorax aristotelis,
tidal stream turbines,
Uria aalge
http://dx.doi.org/10.1111/1365-2664.12646
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