Parasite sought for lake snow

One of New Zealand’s leading scientific experts on lake snow believes it will take years to control its spread, but in the meantime he is researching whether a North American parasite is the answer.

Landcare algal taxonomist and researcher Phil Novis floated the idea of a parasite eating the slimy substance produced by cells of the freshwater alga Lindavia intermedia after reading about other parasites targeting particular strains of algae.

The brown slime known as lake snow was first discovered by fishermen in Lake Wanaka in 2004.

Since then it has spread to more than a dozen South Island lakes and last month it was detected in the Tasman district for the first time.

DNA testing has shown it to be genetically identical to specimens from Lake Youngs, in Washington state in the US.

This week Dr Novis is expecting a delivery of sediment samples from 50 lakes in Washington state from which he plans to extract DNA to find out whether a parasite species that eats lake snow exists in the lakes.

Lake Youngs is a reservoir. The water is slightly treated and it is piped hundreds of metres before entering the lake.

Dr Novis said "there could be a scenario that lindavia is finding its way into Lake Youngs but some kind of control agent (or parasite) is not."

Dr Novis said even if he found definitive evidence of a lindavia parasite from the Washington lakes sediment samples tomorrow, it would be years away from potentially introducing it into the South Island lakes.

"We’d have to establish a strain of it in a culture, we’d have to test it in all sorts of non-target species, and the final decision would rest with the EPA [Environmental Protection Authority]."

However, Dr Novis said the attraction of the biological control route for lake snow was that it did not wipe out other biota and it did not involve changing the toxicology of the water.

"The only difference is one extra species in the lake and there will be chytrids [parasites] and oomycetes [pathogens] in the lake already. It is another addition."

Dr Novis said the really hard part of introducing a biological control was making it acceptable to the public.

He said people probably did not realise how many agents had already been introduced into our environment and how successful they had been.

To date he has not heard of any other measures proposed to control lake snow that "had a chance" without significant adverse effects on everything else.

"We are playing the long game with this," he said.

kerrie.waterworth@odt.co.nz

Add a Comment

 

Advertisement