Do Changes in Current Flow as a Result of Arrays of Tidal Turbines Have an Effect on Benthic Communities?

Abstract

Arrays of tidal energy converters have the potential to provide clean renewable energy for future generations. Benthic communities may, however, be affected by changes in current speeds resulting from arrays of tidal converters located in areas characterised by strong currents. Current speed, together with bottom type and depth, strongly influence benthic community distributions; however the interaction of these factors in controlling benthic dynamics in high energy environments is poorly understood. The Strangford Lough Narrows, the location of SeaGen, the world’s first single full-scale, grid-compliant tidal energy extractor, is characterised by spatially heterogenous high current flows. A hydrodynamic model was used to select a range of benthic community study sites that had median flow velocities between 1.5–2.4 m/s in a depth range of 25–30 m. 25 sites were sampled for macrobenthic community structure using drop down video survey to test the sensitivity of the distribution of benthic communities to changes in the flow field. A diverse range of species were recorded which were consistent with those for high current flow environments and corresponding to very tide-swept faunal communities in the EUNIS classification. However, over the velocity range investigated, no changes in benthic communities were observed. This suggested that the high physical disturbance associated with the high current flows in the Strangford Narrows reflected the opportunistic nature of the benthic species present with individuals being continuously and randomly affected by turbulent forces and physical damage. It is concluded that during operation, the removal of energy by marine tidal energy arrays in the far-field is unlikely to have a significant effect on benthic communities in high flow environments. The results are of major significance to developers and regulators in the tidal energy industry when considering the environmental impacts for site licences.

Comparative Effects of Climate Change and Tidal Stream Energy Extraction in a Shelf Sea

“…Moreover, impacts on benthic communities is also an ongoing topic of research. However, the effect of tidal energy extraction on benthos might be negligible, since their composition is stable over an approximate 1 m/s range of velocities in high‐velocity flow environments (Kregting et al, ), which is above the range of changes we found; an overall habitat loss might instead be predicted to occur in response to climate change.…”

Settlement of Ostrea edulis is determined by the availability of hard substrata rather than by its nature: Implications for stock recovery and restoration of the European oyster

“…The entrance to the south basin is a long narrow channel known as the Narrows, where current tidal velocity reaches ~3.5 m/s (Kregting & Elsäβer, ). It is typified by an exposed bedrock substratum (Kregting et al, ) that spills out into the south basin where a range of substrates can be found, depending on water flow velocity.…”

Providing ecological context to anthropogenic subsea noise: Assessing listening space reductions of marine mammals from tidal energy devices

“…Noise levels produced by two sub-sea tidal turbines were assessed in the Narrows tidal [29]. The seafloor of the Narrows consists of cobbles and small to large boulders on a bedrock base layer, with flow rates at the turbine sites reaching approximately 2 ms -1 [30]. The two tidal turbines considered in this study were the ¼ scale Deep Green sub-sea turbine developed by Minesto (see [13] for full details on this device, referred to herein as the 'kite'), and the full-scale SCHOTTEL IST device ( [8] referred to herein as 'schottel').…”

“…Current velocities were measured with a seabedmounted broadband 600 kHz RDI Teledyne Workhorse Monitor Acoustic Doppler current profiler (ADCP) installed approximately 30m from the kite's position. Bathymetry data was obtained from the Strangford Lough hydrodynamic model [33] and sediment properties were obtained from [30].…”