When one thinks about sound in a marine environment, the clicks and squeals of dolphins, and long songs of the whales comes first to mind. So it would seem logical to think that the acoustic signal from a seismic survey array affects primarily dolphins and whales. While much concern has been over the wellbeing of marine mammals, there exists a wide range of organisms that detect and use sound in the marine environment for their survival, and their survival is of equal importance to that of marine mammals.
Enclosed turtles have shown a strong stress response and subsequent avoidance of airguns used in seismic surveys. They have also experienced reduced hearing sensitivity after being exposed to airgun shots.
Fish have been shown to be sensitive to the acoustic signal of a seismic survey, despite typically having less acute hearing than marine mammals. Effects range from serious ear injury at short range, to behavioural reactions such as dropping to deeper depths, milling around in compact groups, ‘freezing’, or becoming more active. Fish have started avoiding the area surrounding a seismic survey, possibly up to a few kilometres around a survey area. Reduced catch rate per unit effort has been recorded for a variety of fish species, and acoustically estimated fish numbers dropped following seismic survey activity compared to pre-survey numbers. The impacts on fish eggs and larvae include decreased egg viability, increased embryonic mortality, and decreased larval growth.
Invertebrates are also not immune to the effects of seismic survey acoustic signals. Squid have mass stranded with massive internal injuries, and show a strong startle response with ink injection in response to airgun shots. A bivalve species showed altered hydrocortisone, glucose, and lactate levels in response to seismic noise. A scallop species presented body malformations which could affect recruitment of scallop larvae in response to seismic pulses.
This is the third in a series of blogs which looks into the effects of seismic surveys in a marine environment.
Written by: Minke Witteveen
For further reading:
- Gordon, J.C.D., Gillespie, D., Potter, J., Frantzis, A., Simmonds, M.P., Swift, R. and Thompson, D. 2004. A review of the effects of seismic survey on marine mammals. Marine Technology Society Journal 37: 14-32.
- McCauley, R.D., Fewtrell, J., Duncan, A.J., Jenner, C., Jenner, M-N., Penrose, J.D., Prince, R.I.T., Adhitya, A., Murdoch, J. and McCabe, K. 2000. Marine seismic surveys – A study of environmental implications. Appea Journal 40: 692-708.
- Weilgart, L. 2013. A review of the impacts of seismic airgun surveys on marine life. Submitted to the CBD Expert Workshop on Underwater Noise and its Impacts on Marine and Coastal Biodiversity, 25-27 February 2014, London, UK. Accessed: 2017-01-28. URL: https://www.cbd.int/doc/meetings/mar/mcbem-2014-01/other/mcbem-2014-01-submission-seismic-airgun-en.pdf