In 2022, the Scottish Government held its first offshore wind leasing round in over a decade, ScotWind Leasing, and awarded seabed option agreements to a total of 20 offshore wind energy projects. Since the waters around Scotland are home to many marine species, the potential effects of underwater noise from offshore wind construction and operations on marine life remain key considerations in the siting, consenting, and development of new wind farms.
To help address remaining data gaps, the Scottish Passive Acoustic Network (SPAN) project is using an extensive network of passive acoustic monitoring (PAM) stations to collect long-term data on marine mammal distribution, relative abundance, and underwater noise in data deficient areas around the coasts of Scotland and across the ScotWind developments. SPAN is funded by the Scottish Government’s Scottish Marine Energy Research (ScotMER) program, which invests in targeted research addressing evidence gaps to enable and promote the sustainable development of offshore renewable energy.
SPAN commenced in December 2022 as an expansion of the East Coast Marine Mammal Acoustic Study (ECOMMAS), which aimed to monitor the broad scale effects of offshore wind farm construction on marine mammals in Scottish waters, such as the bottlenose dolphin (Tursiops truncatus) and harbour porpoise (Phocoena phocoena). ECOMMAS (which commenced in 2013) deployed acoustic click detectors, known as C-PODs (Cetacean POrpoise Detector), at 30 locations off the east coast of Scotland to detect echolocation clicks along with 10 broadband recorders to record ambient underwater sound levels and cetacean vocalizations. These moorings (Figure 1) are deployed and retrieved using an acoustic release system and remote control, instead of surface markers, avoiding some challenges with lost and trawled gear. With the expansion of offshore wind development around Scotland, ScotMER decided to broaden the study scope to include additional monitoring locations on the western and northern coasts (Figure 2), where less data is currently available. In these new locations, the SPAN team is deploying newer click detectors, known as F-PODs (Full waveform capture POrpoise Detector), and broadband recorders on all moorings. In addition to collecting fine-scale temporal data on marine mammals, the SPAN moorings can also detect fish tagged through other monitoring projects, such as PrePared, which monitors diadromous fish migration routes, and SeaMonitor, which investigates elasmobranch site fidelity.
Figure 1. Scottish Passive Acoustic Network mooring setup with passive acoustic monitoring equipment (click detector and broadband recorder) and an acoustic release system.
Figure 2. Scottish Passive Acoustic Network mooring locations around Scotland.
So far, over 100 gigabytes of click detector data and 120 terabytes of broadband data have been collected and utilized by researchers and renewables developers to incorporate into their research or to augment existing datasets. Several developers have also added their own monitoring stations using SPAN’s mooring setup to gather additional site-specific data. SPAN data are also being used to develop a training course for the open-source software, PAMGuard, and being sent to the OSPAR Commission as part of a North Sea-wide noise monitoring effort. However, the large amount of data being collected through SPAN has translated into storage challenges and highlighted the need for further standardization of PAM metadata, as well as a broad, public repository network that can host PAM data in an organized and accessible format.
Together with ECOMMAS, SPAN is one of the most spatially extensive and longest running marine mammal acoustic monitoring projects in the world, collecting marine mammal and underwater noise data during a period of huge expansion for both fixed-bottom and floating offshore wind energy in Scotland. The data collected will help inform understanding of the potential environmental effects associated with fixed-bottom and floating offshore wind development around the world, while also filling high priority evidence gaps surrounding the distribution of marine mammals in Scottish waters.
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