31. In areas such as the Irish Sea where strong tidal flows prevail, would the presence of multiple large monopile-type structures in the water affect current flows, turbulence, mixing, sediment transport and biological activity in the immediate areas?

Yes. Several studies have indicated the possibility of negative impacts extending for distances of up to 60 km on marine life and marine habitat due to wake formation from turbines located in moving water. Additional sediment in the wake could cause a decrease in underwater light availability, negatively impacting primary production (e.g., phytoplankton survival and growth) and reducing the ability of sight-feeding predators to hunt their prey. It is also suggested that shifts in the patterns of suspended sediment will lead to changes in deposition or erosion patterns, risking reef smothering and increased erosion along Ireland’s coasts.

A 2018 study prepared for the Crown Estate (UK) identifies an increase of 40% in the concentration of suspended material in the wake behind monopile structures in an area where tidal flows were evident and further investigated several factors which would possibly cause increased sediment in the water. The study concluded that, along with scouring of the local seabed and the release of mud and organic material associated with epifauna (animals found to be living on or attached to the seafloor or submerged structures), the redistribution of suspended material from the lower water column to the surface is caused by the increased turbulence within the wake. (A study in the North Sea showed that hydrodynamic disturbance had a major impact on the whole ecosystem. Will try to locate.)