Bubble curtains attenuate noise from offshore wind farm construction and reduce temporary habitat loss for harbour porpoises

Published source details Dähne M., Tougaard J., Carstensen J., Rose A. & Nabe-Nielsen J. (2017) Bubble curtains attenuate noise from offshore wind farm construction and reduce temporary habitat loss for harbour porpoises. Marine Ecology Progress Series, 580, 221-237.
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This study is summarised as evidence for the following.

	Action	Category
	Use acoustic devices to deter marine and freshwater mammals from an area to reduce noise exposure Action Link

Use acoustic devices to deter marine and freshwater mammals from an area to reduce noise exposure

A before-and-after study in 2013 at a wind farm construction site in the North Sea, Germany (Dähne et al. 2017) found that using acoustic devices reduced harbour porpoise Phocoena phocoena activity prior to pile driving within 18 km of the site. At distances of 1.5–12 km and 15–18 km from the site, the average percentage of minutes with porpoise clicks detected was lower during periods in which acoustic devices were used (1.5–12 km: 1–5%; 15–18 km: 3%) compared to before devices were used (1.5–12 km: 4–7%; 15–18 km: 5%). At distances of 12–15 km, the difference was not significant (before: 4%; during: 3%). In February–December 2013, acoustic devices were used during 0.5–4 h periods prior to pile driving for 80 wind turbine foundations. Acoustic devices were Aquatec AQUAmark 100 pingers (emitting sounds at 20–160 kHz) and a Lofitech Seal Scrammer (emitting 0.5 second sounds at 14 kHz). Twelve acoustic detectors placed 1–31 km from the site recorded porpoise echolocation clicks for periods before (3 h) and during acoustic device use (0.5–4 h) for each of the 80 foundations.

(Summarised by: Anna Berthinussen)