Warning: Watch for lake snow

There are fears the sticky algae lake snow could spread from Lake Wanaka to Taupo. Photo / ODT

It's erratic. It's unpredictable. It's quite disgusting. And the worry is that it's coming here.

Lake snow is a sticky, biological material made up of groups of algae that form colonies.

Lindavia intermedia are the algae species responsible for creating lake snow.

It has already colonised lakes Wanaka and Wakatipu in the South Island, creating costly problems. Although lake snow is not toxic and poses no known human health risk, in the water the algae forms a large sticky floating mass, and it secretes a glue-like slime that blocks water inlets and water filters, clogs fishing lines and the inlets on outboard motors.

Residents of Wanaka especially are having to install water filters between their houses and their street water toby at their own expense to stop it blocking shower heads and washing machine filters.

It can also stick to boat hulls and equipment, wetsuits and skin or hair.

Aside from the Otago lakes, lake snow has also been found in Lake Coleridge in Canterbury. In the past, it has been found in Lake Benmore, Lake Aviemore and Lake Hayes in the South Island and Lake Waikaremoana in the North Island.

However it does not appear to be present in these lakes today, and scientists are unsure why. DNA testing shows that it is genetically identical to specimens from Lake Youngs, Washington State, USA.

The prospect of lake snow coming to Taupo has local environmental advocate David 'Didymo Dave' Cade pretty worried, and he's making it a personal mission to raise awareness of lake snow, by talking to people, parking his own hand-painted trailer-mounted sign around the Taupo area and spreading the word on social media.

Dave says lake snow is erratic and unpredictable. While the best-case scenario that it may never arrive in the Taupo district, that can't be taken for granted.

He's especially concerned that visitors coming to Taupo from Wanaka and Wakatipu will unwittingly introduce lake snow algae to Lake Taupo.

Lake snow can be moved as a single-cell organism, and although it can be killed by check, clean, dry methods, Dave says the wider community is largely unaware of the devastation it could bring.

So two weeks ago he donned his best suit and walked the streets of Taupo talking to local businesses about lake snow and its impact.

He says better awareness is needed because many visitors who arrive in Taupo from the South Island will check into their accommodation and then go straight down to the lakefront without realising they need to clean or dry their gear first.

He messaged all the Taupo district councillors about lake snow, although the response was mixed, and says he's like to see a proactive approach to letting people know about lake snow and how they can prevent it.

Conservation Department freshwater threats ranger Brenda Lawson says lake snow is an example of another foreign algae that has made its way to New Zealand and could affect any waterway.

She said the important thing for people to remember was to always check clean dry when moving between waterways to avoid transferring any sort of pest algae, weed or fish. Unchecked spread of pests and weeds had caused massive problems overseas, she said.

"When you look at places like the (US) Great Lakes, they've got pest fish everywhere and nasty razor mussels moving around. It's just caring enough for our environment that we don't wind up with the same problems."

More information about lake snow is at www.orc.govt.nz and check clean dry information can be found at www.mpi.govt.nz (search for 'check clean dry).