Sitting at the Northernmost tip of Scotland, exposed to the North Sea, the Shetland Islands have emerged as a bastion of renewable energy innovation, with tidal turbines harnessing the power of the North Atlantic tides. However, questions about their potential impact on the marine environment have surfaced—more particularly, the influence of such turbines on marine noise levels. To improve the knowledge surrounding tidal turbine contributions to marine noise, researchers are employing state-of-the-art technology, including drift buoys, to measure noise levels generated.
Cutting-Edge Technology
Underwater noise has the potential to affect marine life, from disrupting communication to displacement. To accurately assess and mitigate these impacts, researchers are utilizing advanced hydrophones and acoustic monitoring systems complemented by strategically deployed drift buoys. These buoys enhance the precision of data collection, providing a comprehensive understanding of the noise landscape around the turbines.
To compare the noise generated by three direct-drive tidal turbines versus three conventionally geared turbines, a hydrophone was suspended below a float that housed a high-resolution data logger. The float was tethered to a drifting workboat, and the hydrophone was cabled to a PAM-Go data-acquisition system onboard the boat to enable the acoustic signal to be monitored in real time. This method had advantages over using an independent drift buoy, including:
- In-field adjustments: collection of data could be verified, and adjustments to negate clipping and low signal level can be made.
- Increased control: tethered hydrophones can be monitored for drift speed and location to meet target data collection zones.
Equipped with sensitive sensors, drift buoys were strategically placed in key locations around the turbines. This allowed for real-time monitoring of underwater noise levels, providing a detailed and accurate portrayal of the acoustic environment.
Defensible Results
Findings indicate that Shetland’s tidal turbines operate well within acceptable noise limits. Underwater sound from both the direct-drive and geared turbines was found to be unlikely to result in injury to marine mammals based on the Southall et al. (2019) thresholds. Disturbance may be possible, particularly at close ranges, but based on the sound levels and frequency content, it is considered unlikely that significant disturbance would occur over a wider area. Localized disturbance could be beneficial for reducing collision risk with operational turbines.
This research not only underscores a commitment to sustainable energy practices but also sets a precedent for responsible tidal energy development worldwide. As the tidal energy industry gains momentum in Shetland and beyond, employing drift buoys for monitoring underwater noise levels is a critical step toward responsible and sustainable development. By striking a balance between harnessing renewable energy and safeguarding marine ecosystems, we ensure a brighter, cleaner future for generations to come.
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This feature appeared in Environment, Coastal & Offshore (ECO) Magazine’s 2023 Winter edition Fisheries & Aquaculture, to read more access the magazine here.
