The widespread death of important small marine crustaceans is associated with underwater surveys that use high-pressure air guns, finds a paper published in Nature Ecology & Evolution. The study links these acoustic surveys, routinely used for marine exploration of the seafloor for oil deposits, with a two- to three-fold increase in zooplankton mortality more than a kilometre away from the sound source.
Man-made underwater noise is known to affect marine organisms. For example, the use of sonar has been linked to disruption of whale behaviour. However, the impact of noise on organisms lower down the food web is less well-understood, even though large fish and marine mammals rely on these organisms for food.
Robert McCauley, Jayson Semmens and colleagues measured the impact of seismic air-gun exposure on marine plankton by sampling the water surrounding an experimental air gun in southern Tasmania. They find that, compared to control areas where no gun was deployed, the average abundance of zooplankton caught in nets decreased by more than 60% in the hour immediately after the gun was fired, with 2-3 times more dead zooplankton found following the noise.
This decrease was also confirmed through sonar measurements, which detected a 'hole' in the water more than a kilometre from the sound source, where non-fish organisms were absent. The authors argue that more research is urgently needed to determine the impact of this widely used seismic technology on marine life.