Sea mining effects to be simulated
Difficult underwater experiments should reveal just how seabed life is disturbed
Kscience iwi scientists investigating the impacts of controversial seabed mining are about to simulate the effects, in one of Niwa’s most challenging underwater experiments.
Only two seabed ventures have been developed in New Zealand and both met with staunch opposition.
That was amid concern the operations would disturb sea life at their operation sites, and more widely through drifting plumes of sediment and other environmental effects.
In an MBIE-funded effort to learn more about the impacts, scientists will deploy at least nine high-tech instruments on the seabed on the Chatham Rise, off the Canterbury coast where one company has plans to mine phosphate.
Among the equipment to be placed 500m deep is an underwater glider, three undersea observational platforms known as “benthic landers”, a multi-corer to take sediment samples, seabed moorings, water column sampling equipment, a camera to be towed above the seafloor and a “benthic disturber”.
The plume’s dispersal will be monitored and surveys before and after the disturbance measure effects on seabed animals.
Voyage leader and Niwa principal scientist Dr Malcolm Clark said some of the equipment had not been tried before in such a situation and deploying so many instruments at once was “extraordinarily complex”.
“However, this is very important work that will enable us to provide information about the nature and extent of impacts associated with human activities in the deep sea and the level of resilience of the organisms living there.”
The data collected will help build a picture of how biological communities on the seabed may be affected by the sediment stirred up by mining, as well as bottom-trawl fishing.
Uncertainty about the effects of sediment plumes had contributed to applications for seabed mining being declined, and the plumes were also a big environmental concern for sustainable fisheries certification.
“These activities create plumes of sediment but we don’t know how the sediment affects seabed life as it settles again on the seafloor, and how much deep-sea animals can withstand,” Clark said.
“We are doing this experiment on a small scale on the Chatham Rise but it will give us a much better idea of how environmental managers and industry can work to mitigate largerscale disturbance effects.”
The benthic disturber was about 4.5m-long and contained a pump that mixed sediment with water and turned it into a slurry as it was towed. The slurry was pumped out of a central chimney to create the plume, which would be tracked and monitored. The disturbance would take place over about half a square kilometre of seabed.
The benthic landers would carry Malcolm Clark, principal scientist high-definition cameras, lights and instruments to record physical, chemical and biological activity.
Niwa’s ocean glider and a modified acoustic towfish would follow research vessel Tangaroa, measuring turbidity and the density of the plume, while water samples from inside and outside the plume would be collected.
A towed camera would also record high-definition still images and video of the seafloor, which would be sampled by small coring and sled equipment.
Three seabed moorings were also being installed at an undisturbed control site, where they would remain for a year. The information they recorded would be used for comparison with the disturbed area.
A lab-based programme would provide further information on the resilience of the seabed ecosystem.
The research team planned to collect live sponges and corals and test their resilience to various sediment loads in a lab.
“The field and laboratory studies together will be a powerful combination to address when too much sediment is ecologically significant.”
The project was the first of three.