The potential environmental impacts of controversial deep-sea mining will be investigated in a new multi-million dollar study.
Dr Malcolm Clark, a fisheries scientists at the National Institute of Water and Atmosphere (Niwa), said a lack of knowledge about life on the seafloor and how it could be affected had been one of the major factors that led the Environmental Protection Authority to refuse the two off-shore mining applications lodged so far.
There were particular concerns around impacts from sediment plumes, created by disturbance to the seafloor and mining operations discharging the processed water back into the ocean.
Clark is now leading a $3.7 million programme to tackle the questions.
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, he said.
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.
"Of particular importance, however, is a lack of knowledge of the key species or communities that drive ecosystem function, and when human activities could tip a system from the one we know to something different."
In deep sea environments, this was especially tough to study, given the cost of funding the large ships and technology needed for the research, and the fact that the ecosystems themselves were so large.
Of those research expeditions that had been led, nearly every survey had recorded new species, and there was much more to discover.
Global estimates of the number of known marine species total 250,000 - but scientists believe this figure is only about one quarter of what is believed to really be out there.
While we know more than 15,000 marine species inhabit our coastal waters and ocean territory, it's estimated there may be a further 50,000 yet to be found.
"This means that extensive and detailed biodiversity surveys are required to characterise the baseline conditions of any proposed area before mining can be considered."
The study would test the belief that life is highly sensitive to sedimentation stirred by seabed disturbance, and investigate specific impacts, any differences in resilience and prospects for recovery.
Clark said we already knew what general effects could be expected from seabed mining, ranging from physical damage to the seafloor as it was mined, to those that could affect a wider area, through sediment plumes that could bury animals, or eco-toxic releases that could contaminate environments.
Yet, 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.
But Clark said it could still be assessed how ecosystems responded to decreased light levels, how their feeding or respiration was affected and whether such effects were lethal or could be tolerated for certain periods of time.
The Niwa-led study would combine in-situ observations on the effects of sediment deposition with lab-based experiments.
Areas of the seabed would be disturbed, then closely monitored by ship-based surveys, with sampling to be repeated over time to determine which seafloor communities were more affected than others, and whether species and communities could eventually recover.
The churned-up sediment itself would also be assessed to refine plume models that predict spread, while back in labs, experiments would use live deep-sea coral and sponge species to assess their resilience.
Ultimately, the research would define the levels at which sediment impacts became ecologically damaging and offer insights into how such impacts might be reduced.
Clark expected the study would be mainly used by mining companies as part of impact assessments and management plans, but also by fisheries companies assessing effects of bottom trawling.
But he said the science wasn't being carried out in support of what remains a controversial industry.
"The work is not about advocating for a new industry, but to provide environmental managers with information that is needed to evaluate the nature and extent of potential impacts on deep-sea communities, and what measures could be needed to reduce these effects if mining was allowed to proceed," he said.
"Science around environmental effects of any activity is balanced with social and economic issues, and that is one of the roles of the EPA that requires more information on the long-term sustainability of affected ecosystems."
The study comes as company Trans Tasman Resources (TTR) has drawn fresh protest with a second attempt to mine ironsands on the South Taranaki Bight, two years after its first bid was rejected by the EPA.
TTR executive chairman Alan Eggers has described the area where it wants to extract 50 million tonnes of seabed material each year, in waters 20m-42m deep, as "a largely featureless area of naturally shifting sands and sediments colonised by hardy species of common forms of marine life of no unique or special ecological significance".
Off-shore mining in New Zealand
• No application to mine on New Zealand's sea floor has succeeded. Trans Tasman Resource's first bid failed in 2014 after the EPA raised concerns about the impact on the environment, iwi and fishing interests, and its economic benefits.
• Last year, an application by Chatham Rock Phosphate Limited was also 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.
• Last month, TTR lodged a second application, prompting a protest hikoi led by Taranaki iwi Ngati Ruanui and delivering to Parliament a 6000-signature calling for a moratorium on seabed mining.