Effect of Operational Wind-Turbine Vibration on Surface-Dwelling Invertebrates

Abstract

With the UK aiming to achieve 50 GW of offshore renewable energy by 2030, offshore construction will increase in tandem. The construction noise associated with wind turbine installation has gained much attention over the years, with sound emissions threatening to have an impact on the ecology of marine mammals and fish. During operation, continuous vibration is produced by blade rotation and the operating machinery near the blades (the nacelle) that travel down the external surface of the turbine tower and into the foundation and neighboring seafloor. While vibration is known to affect the behavior and physiology of marine invertebrates, the potential for these seismic interface waves, to impact the animals living on the turbine or the seafloor adjacent to the turbine, has yet to be studied. Due to the difficulty of measuring offshore, in this study, substrate-borne vibrations (seismic waves) from a turbine in operation were measured at a terrestrial wind farm at three different locations (turbine tower, concrete foundation of the tower, and adjacent soil in a 10 m distance) at different wind speeds to assess their potential effect on associated animals, particularly invertebrates. The vibration was highest on the turbine tower, with a maximum vibration recorded at 91.3 mms⁻² (114 Hz). However, most of the values fell below 53 mms⁻². The lowest recorded vibration was found within the soil, with maximum vibration not exceeding 2.1 mms⁻² (50 Hz). The recorded substrate vibration showed little overlap with the known vibration sensitivities of invertebrates at their expected locations. Mussels (Mytilus edulis), regularly found to be attached to the towers of offshore wind turbines, dwell in the intertidal area and are often exposed to air. This study finds that their threshold sensitivity (60 mms⁻²) is generally too low to perceive the measured vibrations of the tower. Similarly, hermit crabs (Pagurus bernhardus) and other decapod crustaceans, which dwell close to the foundation of the wind turbines, based on their sensitivity, are unlikely to perceive the minute seismic waves that are conducted into the sediment. However, under some specific but rare conditions, vibration amplitudes were high enough to be detectable by the marine invertebrates. These measurements, while conducted in terrestrial conditions, indicate potential temporary impacts of wind farm operational noise on associated epifauna. Additional information is needed to confirm the severity of the effects on the marine environment.