Offshore construction using gravity-base foundations indicates no long-term impacts on dolphins and harbour porpoise

Abstract
There are concerns about the short- and long-term effects on cetaceans from offshore construction using pile-driving. Gravity-base foundations and anchored floating turbines are alternative installation methods that may have less impact on cetaceans. In this study, we investigated the response of dolphins (Tursiops truncatus and Lagenorhynchus albirostris) and harbour porpoise (Phocoena phocoena) to the construction of wind turbines using gravity-base foundations off Blyth, Northumberland, United Kingdom using cetacean echolocation recorders (C-PODs). Data were collected at nine sites across 3 years (2016–2018) before, during and after construction. Generalised additive mixed models were used to investigate temporal, environmental, and anthropogenic drivers of dolphin and porpoise occurrence from 143,215 h (5967 days) of C-POD data. The models explained 27% and 30% of the deviance in dolphin and porpoise occurrence, respectively. Overall, the results showed no long-term effect on the dolphin occurrence from the construction of the gravity-base wind turbine array. In contrast, porpoise occurrence increased by 32% and 75%, respectively, in the years during and after construction, compared to the before-construction year. Other predictors of dolphin and porpoise occurrence included month, hour of day, tidal currents and vessel sonar activity. Our findings indicate that wind turbine installation using gravity-base foundations had no long-term effects on the occurrence of dolphins or porpoise and may represent an offshore construction methodology that is less impactful to dolphins and harbour porpoise than impact pile-driven turbine installation methods. These results are important for future offshore energy developments; however, further studies are recommended to investigate potential species and location variations.

Citation
Potlock, K. M., Temple, A. J., & Berggren, P. (2023). Offshore construction using gravity-base foundations indicates no long-term impacts on dolphins and harbour porpoise. Marine Biology, 170(8). https://doi.org/10.1007/s00227-023-04240-1

Acknowledgements
Funding for this study was provided by EDF Renewables (BOD/PR/0081). We would like to thank EDF Renewables for both facilitating and funding this project. We thank the crew of the RV Princess Royal , Neil Armstrong, Barry Pearson, and Liam Rogerson, and the crew of the Northumberland Inshore Fisheries & Conservation Authority vessel, the St. Aidan , for their assistance in C-POD deployments and retrievals. We extend our gratitude to Professor Philip James and Ms. Sarah Kenney for their efforts in building and managing the project database, Dr Joseph Eisaguirre for modelling feedback and advice, Dr Amy Scholik-Schlomer for her input to acoustic measurements and Dr Miguel Morales Maqueda for his assistance in obtaining several of the environmental variables included within our analyses. We also would like to thank Nick Tregenza and Daniel Murphey of Chelonia United Kingdom for assisting with C-POD software and data questions. Lastly, we thank the anonymous reviewers for all feedback and suggestions that went to improve this manuscript. The views and opinions expressed in this paper are those of the authors and do not reflect the official policy or position of the National Oceanic and Atmospheric Administration, the U.S. Department of Commerce, or the U.S. Government.

Publisher
Springer Science and Business Media LLC

Journal
Marine Biology

DOI
10.1007/s00227-023-04240-1

Additional Links
https://link.springer.com/10.1007/s00227-023-04240-1

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