Petroleum Geo-Services, a Norwegian company, has applied to carry out seismic surveys for oil along the Cape’s West Coast, which requires the use of airgun blasts into the sea. This is typically damaging to marine life due to the extreme acoustic disturbances it causes.
The surveying services company plans to make use of 2D and 3D seismic surveys over an area stretching from Alexander Bay to the Cape Agulhas. The surveys may take up to five months to complete and are scheduled to begin in the near future if approved by the Petroleum Agency SA (PASA).
If PASA makes the decision to issue the permit, the environmental impact could be catastrophic. The reason seismic testing can be so harmful to the environment is that it has a disastrous effect on zooplankton, which is the base of the ocean food chain. It also has a strong link to the beachings of whales, seals and dolphins.
However in spite of the negative effect it has on the environment, seismic testing is also a vital aspect of oil and gas exploration.
This process entails bursts of low-frequency impulse signals being discharged into the ocean with an airgun system. The sound-waves bounce off geological formations found on the ocean floor, and are captured and stored by onboard hydrophones.
The data retrieved is then analysed for details about the different types of undersea rocks and signs of a presence of oil or gas within the rocks.
The proposed plan is that a soft-start procedure will be used to ‘warn’ marine life and cause them to disperse from the immediate vicinity before the survey begins so that they remain unharmed by it. This ‘warning’, however, will not be effective for zooplankton, as bigger ocean animals can swim away, but zooplankton cannot drift away quickly enough to get out of harm’s way.
A seismic survey conducted off KwaZulu-Natal coast in 2016 was believed to be linked to the beaching of 10 whales, five seals, and nine turtles as well as the deaths of 42 birds.
Another South African study found that African penguins avoided their regular feeding area when seismic surveys were underway in the area, only returning after the surveys had ended.
Other studies also noted that the impact of acoustic disturbances on marine animals include damage to organs, tissue damage and haemorrhaging. It is also believed to be linked to altered behaviour in whales.
