Biosecurity Minister Jim Anderton confirmed today that every effort was being made through scientific analysis to establish whether the discovery this week of what appeared to be dead didymo cells in surveillance samples collected from six sites on the Tongariro, Whakapapa, Mangatepopo and Whanganui Rivers in the Central North Island confirm the presence of didymo.

Further samples were collected from these rivers and the results showed dead cells at two sites on the Tongariro River only – at Rangipo and Waipakihi. Further testing was conducted both upstream and downstream of these sites. Two negative results, where no dead cells were present, have been received from the Rangipo site. Negative results were also received from the upstream and downstream test samples from Waipakihi.

Further DNA sampling has been conducted at the six original sites, the results from these tests are due by Monday. The DNA analysis method is able to detect didymo at very low levels.

Genesis Energy has voluntarily shut down power generation at the Tokaanu Power Station, as operating the station requires the diversion of water between river systems. We are working with Genesis Energy to assess the risk of re initiating power generation on the Western and Eastern diversions (see map). Power generation will resume on the Western diversion if DNA tests on this system are negative. However, because of a different risk profile, the Eastern diversion will be subject to additional testing before decisions about resumption can be made.

The Tuwharetoa Maori Trust Board has restricted road access to the Tongariro River and surrounding area, including the Waiouru Army exercise area. The Trust Board has explained the situation to the Army, who have agreed not to use this exercise area.

The high number of sites at which dead didymo was found is unusual. MAF Biosecurity New Zealand is investigating whether this might have been the result of cross-contamination during the initial field sampling.

“It’s important to remember that it is live cells that need to be present before a waterway can be confirmed as being infected with didymo,” Jim Anderton said. “But that doesn’t mean that we can relax because the samples have produced only dead cells. We need to find out where they came from and how they got there.”

MAFBNZ is working in partnership with Central North Island agencies, including the Department of Conservation, Fish & Game, Genesis Energy, Tuwharetoa Maori Trust Board, and the New Zealand Recreational Canoeing Association.

“The public are being asked to avoid using these rivers until the results have come in. And I want to take this opportunity to remind all river users all round New Zealand to check, clean, and dry all of their equipment between waterways,” Jim Anderton said.

A Central North Island didymo action group has been in place in the region for the last 18 months and has a response plan that will be implemented, should live didymo be found in the area.

Further information will be announced immediately it is available.

Information about didymo and cleaning methods is available on the MAF Biosecurity New Zealand website: www.biosecurity.govt.nz