Scientists from Cawthron Institute in Nelson are using the $800,000 Autonomous Underwater Vehicle (AUV), nicknamed DORA (Delaware Oceanographic Research AUV), to study the Motueka River plume as it comes into Tasman Bay. The plume, which can extend over 20 kilometres into the Bay, is known to influence water quality and growing conditions for shellfish.
The AUV can provide a unique 3D perspective on how the river plume behaves and guage its effect on salinity, temperature and turbidity in Tasman Bay.
Cawthron Marine Scientist Chris Cornelisen says the AUV's cutting-edge technology will enable them to gather more precise information on how river plumes influence the coastal environment.
"In a single mission, this vehicle is capable of acquiring information not previously obtainable using more conventional and labour intensive methods typically involving instruments deployed from boats."
The scientists are particularly interested in gathering more information on a little-known phenomenon in Tasman Bay: a bottom layer of suspended sediments and phytoplankton, that can appear in the summer and is thought to be linked to the productivity of scallops in the area.
"We will be using the AUV to fly near the bottom within the turbidity layer, gathering a continuous data set of spatial data that will, for the first time, give us a far better appreciation of its extent and potential influence."
The AUV is in effect a miniature submarine, only with a virtual crew. It is 2.7 metres long and weighs just 80 kilograms.
In addition to measuring what's in the water, the AUV is armed with underwater cameras, side scan sonar and bottom mapping sonar for acquiring high-resolution imagery of the seabed, accurate to within 100 millimetres.
Its conning tower contains an Iridium cell phone transmitter to relay data when on the surface and call the scientists by mobile phone when the mission is complete. Chris Cornelisen says it is like nothing else scientists in New Zealand have had a chance to use before and for oceanographers it is the ultimate research tool.
"It is very different to towing an instrument in the water. Once released into the water the AUV flies 'on its own' before returning to base unaided. We can track it using a hydrophone and can modify missions while it's in the water. It's also smart enough to avoid obstacles and stay in any particular area to gather additional information of value without being told."
The AUV, one of 13 worldwide, has been brought to New Zealand by researchers from the University of Delaware who are being co-funded by their University, Cawthron Institute, Waikato University and the Royal Society of New Zealand.
Commercial & Investment Manager, Daryl Wehner says this new collaborative relationship can only strengthen the Institute's ability to provide research, technology and advice for the management of sustainable marine and freshwater ecosystems and resources.
"This in turn can only be of benefit to the region and New Zealand. Cawthron Institute would eventually like to see one of the AUVs permanently housed in New Zealand", he says