Tangaroa sets sail to map the seabed off Otago

 New Zealand's research vessel Tangaroa set sail from Wellington on Saturday to map the seabed off the coast of Otago. The survey area includes the Canterbury and Great South Basins.

The voyage is part of the Ocean Survey 20/20 project, a fifteen-year programme established in 2004. Land Information New Zealand (LINZ), is the coordinating agency of the programme, which aims to provide New Zealand with better knowledge of its ocean territory, including New Zealand's Exclusive Economic Zone (EEZ), continental shelf and the Ross Sea region. This work will help New Zealand better manage and sustainably develop its ocean resources.

The New Zealand Government's Petroleum Action Plan sets out a programme of action to ensure safe and responsible development of New Zealand's oil and gas resources. Investment in seismic surveys helps encourage uptake of exploration permits by the petroleum industry. This survey of the Canterbury and Great South Basins will provide further data to support current and future exploration of the area.

NIWA's General Manager of Research Dr Rob Murdoch says, "Potentially this is an important region for oil and gas exploration. As such there is a need to better map the region through appropriate surveys. This will also help provide a basis for environmental management should oil and gas development in this region proceed."

The area Tangaroa will be working within covers 52,000km2, of which about 50 percent will be covered within the 18-day survey. The area they will be focusing on is the Bounty Channel.

This survey mapping of the area using Tangaroa's Kongsberg EM302 multi-beam echosounder and sub-bottom profiling will provide a physical context for any planned exploratory oil drilling in the future. It will allow creation of a highly accurate digital terrain model of the seabed, showing the materials it is composed of: silts and clays, sands and gravels, rocks and reefs.

The echosounder also has the ability to identify and track significant gas plumes in the water column, indicative of escaping gas.

The data gathered will support future environmental impact and engineering risk evaluations. The design of possible future anchoring systems and offshore/seabed engineering structures will be able to take into account the stability of steep canyon walls in the region. Collected data can be used to further enhance the geophysical knowledge and natural hazard assessments of the area and for nautical charting. Improved nautical charts are important for maritime safety, oceanography and tourism.

The survey data will help provide a basis for any future biodiversity assessment. "We know about what biodiversity is in the shallow area, but we don't know what is in the really deep parts, in the trough," says Dr Murdoch.

The next stage of study will involve the collection of samples for a biodiversity assessment. That assessment can be used to establish an environmental baseline, evaluate the potential environmental effects of any oil drilling, and to help develop any special environmental guidelines specific to the area.

Map of survey area Canterbury and Great South Basins.
RV Tangaroa. [NIWA]