Call for river to be closed over algae fears

The Green Party has called for a North Island river to be closed until scientists have established if it has been contaminated with a devastating algae.

Biosecurity New Zealand is testing a sample of algae that a trout fisherman spotted in the upper reaches of the Rangitikei River and thought looked like the invasive algae didymo.

Didymo is snarling up South Island rivers but has yet to be confirmed in the North.

Biosecurity response manager David Hayes said today he hoped test results would be available tomorrow and was hopeful the algae was a native type that sometimes looked like didymo.

"We've had a number of these in the past however and to date all of those have proved negative," he told National Radio.

"So at this stage its a suspicious find. We won't be taking any direct action until we have a confirmation one way or another." He praised the fisherman for his actions.

But the Greens' biosecurity spokesperson Metiria Turei said Biosecurity New Zealand should err on the side of caution to prevent any chance of the algae spreading.

"There's no point closing the gate after the algae has bolted," she said.

"Didymo has proven that it is able to spread very quickly so we must not sit on our hands awaiting the results of tests. The Rangitikei must be closed as a precautionary measure.

Didymo, also known as rock snot, was first detected in a Southland river in 2004 and now appears in more than 30 rivers and tributaries across the South Island.

Although it is not harmful to humans, its blooms form large, unsightly brown mats which smother riverbeds, affecting food sources for fish and making recreation unpleasant.

A single drop of affected water from damp equipment can spread the algae from one waterway to another and Biosecurity urges river users to wash all equipment.

- NZPA