Giant squid strands after seismic survey
Bioacoustician Michele André et.al. from the Catalonian “Laboratory of Applied Bioacoustics” has published a paper which examines the impacts of low frequency (50Hz–400Hz) noise on cephalopods – squid, octopus, and cuttlefish. Exposed to surprisingly low levels of sinusoid noise their kinosensory cells were catastrophically damaged.
These “hair cells” or cilia are associated with the animal’s sense of location and balance, and in other animals are associated with sound perception.
What is particularly alarming about these results is that the exposure levels of 157dB–175dB (re:1μPa) is the equivalent acoustical energy level that you would encounter on “band night” in your local pub (95dB –112dB re 20μPa). And unlike the nasty sonar and digital communication signals associated with Navy related strandings, these critters were exposed to fairly benign sine waves.
Given that the typical Navy and seismic survey mitigation practices call for exposures to remain below 185dB re:1μPa (ten times louder than the maximum exposures in the study) there is a high probability that cephalopods world-over have been damaged by anthropogenic noise.
In the paper the following question is asked: “Because invertebrates are clearly sensitive to noise associated with human activities, is noise, like other forms of pollution, capable of affecting the entire web of ocean life?”
What remains to be determined is if the impact is due to some relationship between “particle motion” and “pressure gradient” acoustical energy. These characteristics play into animals sensing sound-source proximity and it could be that the closeness of the lab signals may have different impacts than equally loud exposures generated from further distances.
I hope in this last question we can find some good news.