The widespread use of air guns in underwater seismic surveys could be dramatically reducing populations of the microscopic animals at the base of the marine food chain.
Plankton are vital for the health of ocean ecosystems, but their sensitivity to human-made noise is not well understood. Robert McCauley at Curtin University in Perth, Australia, and his team decided to investigate the effects of air-gun signals, similar to those used for the detection of oil reserves, in a bay in Tasmania. They towed nets through the water before and after firing an air gun, and found that the abundance of collected zooplankton fell by more than 60% within an hour of the noise impulse, and that the number of dead animals more than doubled.
Sonar measurements suggest that zooplankton abundance dropped more than a kilometre away from the source of the gun shot.