Offshore energy companies based in Aberdeenshire, Scotland, towed a massive floating wind turbine back to port for maintenance.
The disconnection and towing of the floating structure resulted in an increase in underwater sound intensity levels up to 29 decibels within the surrounding sea.
Acoustic monitoring has shown that the presence of towing vessels near the wind farm resulted in a 33 percent reduction in harbor porpoise detections.
Turbine maintenance results in periodic sound disturbances that temporarily disturb marine life.
Disconnecting floating turbines for major offshore overhauls
Floating wind farms along the Scottish coast require a lot of maintenance, especially after they have been operating for several years.
Engineers needed to remove the thick metal cables, along with electric cables underwater, to disconnect the floating structures from the seabed.
Tugboats towed these huge floating structures of 820 feet across the sea.
Dragging these massive floating objects to port eliminates the risks of offshore repairs in the heavy North Sea waves.
This buzz of marine vessel activity turns a quiet offshore wind farm into a temporarily busy shipping route.
Dragging these massive wind turbines to port moves the risk from the offshore zone to the coastal zone.
Measuring underwater noise spikes during heavy vessel operations
The submerged hydrophones surrounding the wind farm location continuously measured background underwater sound levels prior to and during maintenance.
The diesel engines and powerful towing winches increased the underwater noise levels by 29 decibels above the baseline.
The sound waves created by the low-frequency propellers travelled several miles in the shallow marine water column.
High underwater sound levels block important acoustic information used by marine mammals to navigate and hunt.
The high noise levels transformed the calm foraging ground into an acoustic battlefield for local marine animals.
An underwater wall of sound was created by industrial vessels.
Tracking harbor porpoise displacement around active work zones
Biologists used passive acoustics to listen for the presence of harbor porpoises in the region during the maintenance of the wind turbines.
The porpoise echolocation in the region decreased by 33 percent during the towing of the tugs and service boats around the wind farm.
The presence of underwater sound forced marine mammals to leave their feeding grounds.
Acoustic detections returned once the heavy maintenance vessels completed towing in the offshore area, according to the University of the Highlands and Islands.
Evaluating unique maintenance demands of floating wind technology
The fixed-bottom offshore turbines mounted on the seabed have component repairs done offshore with the help of jack-up vessels.
Deepwater offshore floating turbines are placed in water too deep for jack-up ships to reach, hence the need for disconnecting and long ocean trips for some types to be maintained.
Tow-to-port repair results in a lot of ship movement and underwater noise over a few weeks.
Developers of offshore energy must schedule their maintenance activities to avoid noise pollution.
Floating energy installations lead to new sounds in the marine environment that need specific handling.
Floating energy resolves depth limitations but poses different challenges with regard to maintenance.
Defining the limits of initial floating wind maintenance studies
Towing floating turbines is associated with temporary displacements of the local population of harbor porpoises.
Although the data gathered is important, it is limited to a small group of five turbines and does not explain all the possible consequences of commercial wind farm noise pollution, especially over larger arrays.
It is unknown if prolonged exposure to such acoustic disturbances results in a permanent change of the habitat or lower reproductive rates of affected animals.
Environmental monitoring of subsequent maintenance procedures will show if seasonal regulation helps to avoid harm to marine wildlife.
The full study can be read here: Caitlin B Harris, Steven Benjamins, Nienke van Geel, Ellen White, Beth Scott, Benjamin J Williamson, Impacts of large-scale maintenance of a floating offshore wind farm on noise levels and harbour porpoise activity, ICES Journal of Marine Science, Volume 83, Issue 8, August 2026, fsag150, https://doi.org/10.1093/icesjms/fsag150
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