Benthic habitats in a tide-swept channel of the Pentland Firth and their potential responses to a tidal energy development

  • Astrid Harendza

Student thesis: Doctoral ThesisDoctor of Philosophy (awarded by OU/Aberdeen)


This thesis investigates sublittoral epibenthic assemblages, the ecological processes associated with distributions of benthic assemblages and potential ecological impacts arising from the de- ployment of tidal energy devices (TEDs) at a key tidal energy development site. An extensive field campaign was undertaken to collect fine-scale, in-situ data for local hydrodynamics, seabed
structure and epibenthic assemblages. Data from a two-dimensional hydrodynamic model com-plemented in-situ flow data and provided an insight into possible changes to local tidal patterns after the deployment of a tidal array. The study revealed a highly complex tidal stream structure with maximal velocities reaching 4.2 ms−1 during spring tide. The seabed was predominantly formed by scoured bedrock. Deployment of a tidal array was predicted to decrease tidal flow within and downstream of the array by up to 24 % for peak flows, whereas effects on the seabed were thought to be minor. Epibenthic assemblages were typical for tide-swept channels with a
fringe of dense kelp forest along the shallow, sheltered waters of the channel, followed by a ’tran-sition zone’ dominated by foliose red algae in the mid-depth ranges and animal turf assemblages in the deeper, very tide-swept waters. Multivariate analyses identified depth and bed-shear stress
as being strongly associated with the distribution and composition of assemblages. In conjunction with presence-only data for epibenthic species, depth and bed-shear stress were used as predic-tor variables to develop site-specific habitat suitability models (HSMs) for a baseline and TED
deployment case. Comparison of probability of occurrence values between the respective HSMs indicated a potential increase of suitable habitat for species inhabiting the deep, very tide-swept circalittoral following the deployment of TEDs, whilst assemblages along the fringes of the channel were mostly unaffected. This is the first attempt of using HSM as a tool for identification of
potential changes in distributions of benthic species arising from the deployment of TEDs. The good overall performance of the models shows this tool may be valuable for for impact analysis of tidal energy development projects.
Date of Award14 Nov 2014
Original languageEnglish
Awarding Institution
  • University of Edinburgh
SponsorsUK Centre for Marine Energy Research, Scottish Funding Council & Highlands and Islands Enterprise
SupervisorAngus Jackson (Supervisor), Mark Sheilds (Supervisor) & Jonathan Side (Supervisor)

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