New study from University College Cork increases concerns over ocean noise impacts.

In spite of the worsening climate crisis, the petroleum industry is still searching for unknown hydrocarbon deposits in the seabed. Hydrocarbon exploration uses airguns fired by seismic survey vessels, which produce pulsed, high intensity noise with deafening sound source levels of 248–255 dB. Such airguns – up to 48 per vessel – are “fired” every 10 to 15 seconds, 24 hours a day, for weeks or even months.

The body of evidence on the negative effects of seismic surveys on cetaceans and other marine species from krill to fish is compelling and steadily growing. Recently, researchers of the University College Cork, Ireland, added another important piece of science. They carried out the first study combining cetacean surveys from seismic survey vessels with other cetacean surveys as control data, thereby taking a multi-species, large-scale approach to examining the effect of seismic surveys on cetaceans, while also accounting for the potential influence of spatial, environmental and temporal variables.

The researchers modelled over 8,000 hours of cetacean survey data across a large marine ecosystem covering more than 880,000 km² in the Northeast Atlantic, a diverse marine environment both in term of habitat and species richness, and home to over 40 marine mammal species.

They found a significant effect of seismic activity across multiple species and habitats, with an 88% (82–92%) decrease in sightings of baleen whales, and a 53% (41–63%) decrease in sightings of toothed whales during active seismic surveys when compared to control surveys. The decrease in sightings was particularly large in the offshore waters to the west and southwest of Ireland, an area identified as of relative importance for cetaceans.

In addition the researchers found it likely that received noise levels may exceed thresholds for eliciting behavioural responses in cetaceans over much larger distances than the visual range of observers on survey vessels.

OceanCare is concerned about the continued hydrocarbon exploration activities around the world and calls on governments to develop and implement a phase-out strategy for such activities, as well as to immediately prohibit any such activity within critical habitat for acoustic-sensitive species. Activities generating intensive ocean noise are proven to negatively impact dozens of marine species. Reducing seismic activities would lower noise emissions in the oceans, and is necessary for addressing the climate crisis: Hydrocarbon resources should remain in the ground.

Source: Seismic surveys reduce cetacean sightings across a large marine ecosystem. A.S. Kavanagh, M. Nykänen, W. Hunt, N. Richardson & M. J. Jessopp Nature | Scientific Reports (2019) 9:19164 | https://doi.org/10.1038/s41598-019-55500-4