SEISMIC surveys could spell disaster for the ocean’s microscopic animals at the bottom of the food chain, essentially jeopardising ocean life as a whole.
These were the findings of a new study looking into the effects of powerful sound waves created during offshore surveys for oil and gas.
Seismic surveys blast compressed air to produce pulses of sound that can probe the sea floor thousands of metres down, for natural resources.
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The study found that, at 220 – 250 decibels, the pulses produced from these blasts are louder than a Saturn V rocket during launch.
Zooplankton, the collective name for the ocean’s microscopic animals, are thought to be most at risk from seismic surveys.
Damage to these creatures could have a devastating effect on the ocean’s top predators and commercially important fish species which depend on Zooplankton for food.
Scientists have known for decades that whales and other marine mammals that use sound to communicate change their behaviour in response to such noise, but this is the first study revealing the harm to Zooplankton.
‘It could be that our focus has kind of been blinkered because it’s been on whales,’ said lead author Jayson Semmens, a marine biologist at the University of Tasmania in Hobart, Australia. ‘Invertebrates are the forgotten ones.’
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Semmens and his team conducted their study off the south-eastern coast of Tasmania in 2015 and their findings were published in Nature Ecology and Evolution.
Using sonar and nets to assess Zooplankton populations, the scientists found that Zooplankton abundance dropped by 64% within one hour of the blasts.
The proportion of dead Zooplankton increased by between 200% and 300% for up to 1.2km away, which was the extent of the research distance.
While the study did not pinpoint exactly how airgun blasts kill Zooplankton, Semmens said the noise probably damages the highly sensitive hair-like receptors that the animals use to navigate.
He is planning a follow-up study with a full seismic air gun setup similar to that used in industrial activities to determine how far the effects of the noise extend.
Semmens and his team also want to look at the exact physical effect of these blasts on Zooplankton.
