[MARMAM] new publication on bubble curtains, pile-driving and porpoises

Michael Dähne michael.daehne at gmx.com
Sat Sep 30 00:47:48 PDT 2017

Dear colleagues,


my co-authors and I are pleased to announce the publication of the following


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

Michael Dähne, Jakob Tougaard, Jacob Carstensen, Armin Rose, Jacob

Marine Ecology Progress Series 580, 221-237.


Effects of constructing the DanTysk offshore wind farm (German Bight, 80
turbines, 6 m diameter foundations) were studied by passive acoustic
monitoring of pile-driving noise and harbour porpoise Phocoena phocoena
echolocation. An acoustic deterrence device (seal scarer) was used to
protect porpoises from hearing loss and bubble curtains were used to
attenuate the pile-driving noise. Porpoise occurrence, quantified by
echolocation signals, decreased when the seal scarer was engaged, during
pile driving and up to 5 h after pile driving stopped. This effect extended
out to 12 km, less than the 18-25 km reported from other pile drivings
performed without bubble curtains. The bubble curtains thus effectively
reduced the temporary habitat loss and risk of hearing loss. The 2 bubble
curtains each attenuated the noise by between 7 and 10 dB, when used
separately, and 12 dB when used together. Attenuation was most pronounced
above 1 kHz, where the pile-driving noise at larger distances was comparable
to or lower than ambient noise. This suggests that noise regulation should
be based on frequency-weighted sound levels in addition to broadband levels,
to assure that mitigation measures are effective in reducing impact on
animals and not only in fulfilling legal requirements. The strong reaction
to the seal scarer raises concern that it may surpass the reactions to the
pile-driving noise itself, when operating with bubble curtains, and calls
for a re-evaluation of the specifications of seal scarer sounds.


The article can be downloaded from


Best regards,

Michael Dähne


Michael Dähne

Curator of Marine Mammals

German Oceanographic Museum



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