Man-made noise ‘drowns’ sea life

It has always been noisy under the sea, but now the sound levels are going through the roof.

The crash of waves, the shifting of the earth’s crust, the clicking of snapping shrimp and the songs of whales are being drowned out by shipping traffic, drilling and dredging, and sonar and seismic surveys, studies show.

And it means even the iconic coelacanth is in trouble.

Addressing the 5th African Marine Mammal Colloquium on Wednesday, Ezemvelo KZN Wildlife scientist Dr Jennifer Olbers said this clamour of human activity – and in particular seismic survey noise related to offshore oil and gas exploration – was harming marine life in various ways.

While relatively little research had been done on the issue in South African waters, the data from the North Atlantic was abundant, she said.

“The level of undersea noise increased by 10-12 decibels between 1960 and 2004.”

She said it was clear the present mitigation measures for seismic surveys in SA were insufficient and the department of mineral resources should not rule on environmental assessments of mining projects.

“It’s certainly not too late but we need to act fast.”

Olbers’s call coincided with a statement from the Centre for Environmental Rights on Wednesday hailing a new report by the South African Human Rights Commission (HRC) challenging the power of the mineral resources department to assess mining projects – including offshore exploration.

With seismic surveys, arrays of air guns towed behind a research vessel fire into the water. The sound vibrations bounce off the sea bed, capturing information about mineral deposits beneath the seabed, and return this information to receivers on the surface.

Olbers said research showed the excessive undersea noise could directly injure or kill marine animals, immediately or over a period of time, by impairing hearing, triggering the release of stress-related enzymes and damaging tissue.

But scientists were equally worried about the indirect effects of seismic surveys.

“These include changes in the behaviour of predator and prey, changes in the way marine animals vocalise – and masking, where sounds of interest are obliterated.”

Studies showed seals were hauling out more from the sea and had stopped feeding in some instances, and the internal ears of fish swimming up to several kilometres away from seismic surveys had been harmed, she said.

“With fisheries, there have been reduced catch rates and decreased abundance in the North Atlantic.

“Closer to home, the Namibian fishing industry reported its tuna catch decreased by 83% from 4,046 tons in 2011 to 650 tons in 2013.”

A study last year in Tasmanian waters showed that zooplankton, underpinning all marine life, suffered “a significant mortality” in the vicinity of seismic surveys.

Olbers said firm intervention was needed.

“We need a national Strategic Environmental Assessment to consider all social, environmental and economic costs and benefits in the short and long term, specifically for the offshore oil and gas sector.”

It was also not advisable for the mining department to oversee environmental authorisations as was presently the case, and a full environmental impact assessment overseen by the department of environmental affairs needed to be instituted for even the reconnaissance phase of mining projects.

Following its study on the nexus of mining and community, the HRC found that “the department of mineral resources is not the appropriate authority for granting and enforcing environmental authorisations with respect to mining”.

It also cautioned against prioritising the immediate economic benefit of mining activities over the protection of the environment.

‘Undersea noise increased by 10-12 decibels between 1960 and 2004’ Dr Jennifer Olbers

EZEMVELO KZN WILDLIFE SCIENTIST