Evaluation of influence of offshore wind farm noise on fishes and dolphins

The use of fossil fuels has affected both land and ocean environments, leading to a growing need for clean and affordable energy sources to reduce greenhouse gas emissions. In particular, offshore wind energy as a form of blue energy is rapidly developing in recent decades. However, the boom of offshore wind farms has raised concerns about the impact of the radiating underwater noise on marine inhabitants during both construction and operation, especially those sound-dependent organisms.

Against this backdrop, a team of researchers led by Professors Zhongchang Song and Yu Zhang from Xiamen University collaborated Senior Scientist Honghui Huang and his team from the South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, to conduct field measurements of the underwater noise of an offshore wind farm in the Pearl River Estuary. They developed an impact-zone estimating model to evaluate the impact zone of the wind farm noise for the fishes and dolphins in the Pearl River Estuary.

Notably, acoustic analysis results showed that the low-frequency operational noise (below 2.5kHz) of wind turbine was significantly lower in the intensity than the broadband pulsed pile driving noise produced during construction, which had a mean zero-to-peak sound pressure level up to 195.1 dB (re 1 μPa) (n = 238) at 30 m from the construction site.

“The Pearl River Estuary is home to the largest group of Indo-Pacific humpback dolphins in the world and our acoustic recordings showed a high diversity of biological acoustics in the wind farm, including fishes, snapping shrimp, finless porpoises and the Indo-pacific humpback dolphins,”  shares Song, who serves as the lead author of the study published in the KeAi journal Water Biology and Security. “The intense pile driving noise during construction of wind farm surpassed the hearing thresholds of the fishes and Indo-pacific humpback dolphin by far, and will inevitably induce negative impacts on these animals.”

To assess the impact scopes of the pile driving noise on marine animals, the researchers developed an impact-zone estimating model base on the cumulative sound exposure level. By referring to established noise exposure metrics, the impact zone of pile driving noise for fishes was estimated to be 12.8m. As for the Indo-Pacific humpback dolphins, the permanent (PTS) and temporary threshold shift (TTS) zones were predicted to be 32.4 m and 580.9 m, respectively.

“Our approach and findings enable us to better protect the local marine life from the effects of pile driving noise radiation, and guide the development of management policies during the construction of offshore wind farm,” adds Song.

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Contact the author: Zhongchang Song, Key Laboratory of Underwater Acoustic Communication and Marine Information Technology (Ministry of Education), College of Ocean and Earth Sciences, Xiamen University, Xiamen, China, songzc@xmu.edu.cn

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