Storage containers cause of dead didymo cell spread

"Contamination of water sampling containers was almost certainly the source of the dead didymo cells found in four central North Island rivers in late October," Biosecurity Minister Jim Anderton announced today.

The finding is the result of investigations by both MAF Biosecurity New Zealand and the National Institute of Water & Atmospheric Research (NIWA) into the origin of the dead didymo cells reported from the Tongariro, Whakapapa, Mangatepopo and Whanganui Rivers as part of Genesis Energy's monthly water quality sampling programme. Subsequent sampling found no further didymo cells - dead or alive - in the rivers.

"The investigations found that pottle lids sent to Turangi were contaminated with microscopic amounts of dead didymo cells. The lids were held in storage in a laboratory at the NIWA facility in Christchurch, prior to being sent to the North Island for use in sampling," Jim Anderton said. "At the time, the laboratory was being used to weigh dried, freeze-dried, and burnt (dead) didymo samples as part of other research projects. The lids were then used to seal pottles used to collect water samples.

"It is important to note that at no time could live didymo cells have been transferred from the NIWA facility to the North Island. Laboratory and sampling procedures are put in place to prevent the transfer of live material," Jim Anderton said.

"While I am pleased that we have found the source of the dead didymo cells reported from the North Island, the episode shows how easy it is for microscopic amounts of didymo to be unwittingly moved from one place to another.

"This afternoon I have spoken to the Chief Executive of NIWA, John Morgan, and expressed the government's concern at the situation. John Morgan has assured me that there has been a full investigation and that steps have been taken to ensure that this will not occur again.

"As well, at the time of the incident there was some speculation that the Army might have been involved in some way with the presence of the dead cells. That has been proved to be wrong and I would like to publicly apologise for the concerns this episode caused to the Army," Jim Anderton said.

The investigation was carried out in conjunction with Genesis Energy, with cooperation from their surveillance and diagnostic contractor, NIWA. Both the MAF and NIWA investigation reports recommend that additional, more stringent measures are put in place for the storage and supply of equipment used in didymo sampling.

Further surveillance is being carried out in the Tongariro area, on top of the regular monthly surveillance that is already in place. Thorough sampling by NIWA showed that no didymo cells were found on any other equipment associated with the Turangi sampling.

"Given the extreme sensitivity of the tests used to detect didymo, there is always the risk of false positives. The tests have been designed in this way to ensure we detect didymo at the earliest opportunity. While no live didymo cells were reported during this episode, MAF Biosecurity New Zealand will continue to treat all initial test results seriously and be open and transparent about such investigations," Jim Anderton said.

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