Chatham Counts on NIWA Ocean Study

Benthic lander fitted with high definition cameras, lights and instruments to record physical, chemical and biological activity. Photo: NIWA

NIWA (National Institute of Water and Atmospheric Research) has launched one of its most challenging scientific underwater experiments this month on the Chatham Rise.

Chatham Rock Phosphate said that this expedition is particularly relevant to its proposed marine phosphate recovery operation on the Chatham Rise.

At least nine separate specialised pieces of equipment will be deployed from NIWA’s research vessel Tangaroa, in water up to 500 meters deep.

The equipment includes an underwater glider, three undersea observational platforms known as benthic landers, a multi-corer to take sediment samples, seabed moorings, water column sampling equipment, an underwater camera that will be towed above the seafloor and a “benthic disturber”.

The aim of the voyage is to disturb a small area of the seabed and create a sediment plume using the benthic disturber. The dispersal of the plume will then be monitored, and surveys before and after the disturbance will measure the effects on the seabed animals. The data collected will be used to build up a picture of how the biological communities on the seabed may be affected by the sediment stirred up by mining or bottom trawl fishing.

Uncertainty about the effects of sediment plumes has contributed to applications for seabed mining being declined and the plumes are also an 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. 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 larger-scale disturbance effects,” NIWA scientist Dr Malcolm Clark noted.

Chatham Rock Phosphate CEO, Chris Castle, said: “Clearly the outcomes of the disturbance research are incredibly relevant to our project in that they will provide real data on the behaviour and effect of plumes generated when the seafloor is disturbed (by any activity including dredging, mining and bottom trawling).

“We have already spent very considerable sums modelling how the plumes will behave so we expect that this real data will further strengthen our ability to quantify these effects.

“We have been involved with the planning of this project, and have a representative on board the Tangaroa to help carry out studies with the NIWA team. We also have other consultants that will be remotely monitoring some oceanographic data as it is generated that could assist the survey planning.”

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