A researcher who has uncovered new insights into New Zealand's ocean environment says seafloor communities need better protection against any future deep-sea mining.
No companies have yet been granted permits to mine seafloor massive sulphide (SMS) deposits deep below the ocean within New Zealand's six million sq km Exclusive Economic Zone (EEZ).
Within the EEZ, these deposits - the product of hydrothermal activity and which can contain, copper, zinc, gold and silver - form at volcanoes one to two kilometres below the sea surface along the Kermadec Volcanic Arc, extending about 2500km north of New Zealand.
While the Kermadec Arc is designated as "prospective" for SMS mining, it is currently reserved from permitting.
While there have been applications to prospect for SMS there, these have been withdrawn.
Victoria University researcher Rachel Boschen, who has been working with Niwa scientists to investigate the environmental effects of any deep-sea mining, said little was known about the seafloor communities found there.
Part of her research involved reviewing 70 hours of video footage covering more than 50km of seabed across three seamounts on the Kermadec Volcanic Arc.
From the footage, Boschen was able to characterise the structure and distribution of seafloor communities.
SMS deposits were formed by hot springs on the seafloor, which were known to be an important habitat for specially adapted animals, she said.
"What I didn't expect was that not only did the areas with active hot springs support unique communities, but areas where springs are no longer active also hosted unique communities."
These communities had complex distributions, with each of the studied seamounts supporting communities not found on the other seamounts.
"The action of the hot springs causes SMS deposits along the Kermadec Volcanic Arc to be rich in copper, zinc, lead, gold and silver, and there has been interest in mining them," Boschen said.
"If mining occurs, the unique communities found in my study could be at risk.
"To mitigate the impacts of any future mining, it's important to designate protected areas that conserve seabed hosting unique or particularly sensitive communities to ensure they are not lost from the region."
Animal collections taken during the study also allowed Boschen to determine the connectivity of populations of a deep-sea mussel species found at seafloor areas at risk from mining.
She examined the DNA of seven populations of a mussel species endemic to active hot springs along the Arc, to assess the populations' genetic connectivity across the species' 830km range.
"By looking at their DNA I was able to determine how connected different populations are along the arc.
"The results suggest that although connectivity is generally high amongst populations, some central populations may play an important role in maintaining connectivity in the region."
Another population at the northern extent of the species' range was less connected and could be more at risk from deep-sea mining disturbance.
"The results indicate that to preserve the connectivity and health of these deep-sea mussel populations, we need multiple protected areas of seabed, designed as a network."
She added a protected network should include SMS sites that are both thermally active and inactive to protect the range of communities and include sites key to population connectivity.
While the Government's proposed 620,000sq km Kermadec Ocean Sanctuary, announced last year, was "a big step towards protecting areas potentially at risk from deep-sea mining", it may not be enough to safeguard unique communities from mining activities, Boschen said.
"There are many SMS deposits south of the proposed sanctuary that are not offered adequate protection, including the seamounts in this study and some other sites on the Arc that are important to regional population connectivity."
One of the supervisors of her research, Dr Malcolm Clark from Niwa, is leading a $3.7 million programme supported by the Marsden Fund to explore the potential environmental impacts of controversial deep-sea mining.
While the Government has stated a strategic priority to reap benefits from seabed resources, the sustainability and integrity of the natural environment also had be maintained, Clark said in a recent interview with the Herald.
What we know about the structure of deep-sea communities remained limited, Clark said; it's estimated that only 20 to 30 per cent of the seafloor species have been formally described.
Because deep-sea mining had not yet taken place anywhere in the world, the actual effects were uncertain.
Most studies to date had focused on the direct impact of disturbance, and there had been little work looking at the effects of sedimentation from deep-sea mining.
Work that had been carried out in shallow water couldn't be applied to what might be expected in deep-sea habitats, where effects would vary between sites and depths.
Environment Minister Nick Smith said a "robust regime" put in place with the EEZ Act in 2013 ensured requirements for any permits or checks on seabed mining in the EEZ.
"There have been four substantive applications since, with two approved and two declined.
"This shows the system is taking a balanced approach."
The EEZ Act also ensured any seabed mining in New Zealand operates within the country's international obligations under various conventions, Smith said.
"Any proposal involving areas including the seafloor communities identified in the study would be thoroughly assessed under an independent assessment process under the EEZ Act."
Off-shore mining in New Zealand
• Mining activities in the Exclusive Economic Zone (EEZ) and Continental Shelf (CS) are regulated by the Exclusive Economic Zone and Continental Shelf (Environmental Effects) Act 2012 (EEZ Act). The EEZ is the area from 12 to 200 nautical miles offshore and the CS is the seabed and subsoil from the 12 nautical mile limit out to the end of New Zealand's submerged landmass.
• Under the EEZ Act, the disturbance or removal of material from the seabed and the deposit of tailings to the sea floor as a result of the mining activity are restricted activities and require a marine consent from the Environmental Protection Authority (EPA).
• Last year, an phosphate mining application by Chatham Rock Phosphate Limited was rejected, with the EPA concluding its operation would cause "significant and permanent adverse effects" on the seabed environment at its proposed site on the Chatham Rise off the coast of Canterbury.
• Trans Tasman Resources has re-applied to the EPA to mine iron ore off the Taranaki coast, after its first bid failed due to concerns about the impact on the environment, iwi and fishing interests, and its economic benefits. Iron-sands seabed mining is different from deep-sea mining.