Marine exploration studies. (Photo: Institute for Marine and Antarctic Studies - IMAS)

Petroleum exploration could increase zooplankton mortality

AUSTRALIA
Saturday, June 24, 2017, 01:40 (GMT + 9)

A team of researchers from Tasmania has found that the air gun signals commonly used in marine petroleum exploration had significant negative impact on the zooplankton stocks, causing an increase in mortality from 18 per cent to 40-60 per cent.

These scientists, from the Institute for Marine and Antarctic Studies (IMAS) and the Centre for Marine Science and Technology (CMST) at Curtin University, studied the impact of commercial seismic surveys on zooplankton populations by carrying out tests using seismic air guns in the ocean off Southern Tasmania.

Through new this new research, whose results were published in leading science journal Nature Ecology and Evolution, impacts were observed out to the maximum 1.2 kilometre range tested, 100 times greater than the previously assumed impact range of 10 metres, and all larval krill in the range were killed after the air gun’s passage.

“Zooplankton underpin the health and productivity of global marine ecosystems and what this research has shown is that commercial seismic surveys could cause significant disruption to their population levels,” points out lead author, Curtin University and CMST Associate Professor Robert McCauley.

IMAS Associate Professor and research co-author Jayson Semmens said a series of sonar lines run perpendicular to the air gun line were monitored prior to, and immediately after the air gun run.

"These sonar runs 'imaged' the zooplankton, and showed a lowered zooplankton presence starting 15 minutes after the air gun passed, with a large 'hole' in the zooplankton evident 30 minutes after the air gun pass,” details Semmens.

This 'hole' or region of lowered zooplankton presence was symmetric about the air gun line and increased through time.

The abundance levels of living and deceased zooplankton were also tested in the same area, before and after the seismic survey testing.

“We counted the number of live and dead zooplankton collected in nets using a special staining technique and found that two to three times as many zooplankton were dead following the air gun operations than those collected before,” stresses Semmens.

Deborah Steinberg, an ecology professor at the Virginia Institute of Marine Science who was not involved with the study, said it is hard to know whether airguns used in the United States would have the same effects as were seen in Tasmania.

“It’s also hard to know why the plankton died in such large numbers. It’s reasonable to assume the results have implications for other regions,” Steinberg said.

In her view, rules are often put in place requiring temporary work shutdowns when whales and other protected animals are detected close to survey vessels, or when they are expected to be migrating through the area. Such protections do little to protect plankton, however, which can be omnipresent.

Steinberg insists that with fewer of these tiny animals in the sea, larger fish, sea lions, seabirds and other wildlife could go hungry more often, reducing populations and fisheries hauls.

For her part, Kristen Monsell, an attorney at the Center For Biological Diversity pointed out that if the federal government does not analyze the likely effects of acoustic testing on plankton prior to granting Atlantic permits, given the findings from Tasmania, “that will create legal vulnerability on their part."

 
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