Habitat mapping of a key tidal energy development site using underwater acoustic and remote sampling

The Pentland Firth, located between the North coast of mainland Scotland and the Orkney Islands, is an area with excellent potential for generation of tidal energy. With the first deployment of tidal-stream energy devices (TED) anticipated by 2013, the need for ecological and physical baseline data is essential to assess possible ecological impacts. As the first part of an extensive benthic habitat mapping study, this paper provides an insight to tidal flow and types of seabed in the Inner Sound of Stroma, a sub-channel of the Pentland Firth with a designated capacity for tidal-stream energy of 400MW. Tidal-stream velocity and direction were measured during different stages of the tide using a vessel mounted Acoustic Doppler Current Profiler. A high resolution Chirp sidescan sonar was applied to gather information on the seabed structure. This study marks an important first step in defining and understanding the physical environment of benthic habitats in these extraordinary, energetic surroundings. Based on these data, further investigations will link physical variables with biotic data and thus facilitate formulation of better hypotheses regarding potential physical and ecological impacts arising from installation of TEDs.