Lindavia intermedia

Sites tested for Lindavia intermedia

Site	Sampling	Present (Y/N)
Lake Moawhango	Sampled in Moawhango River	Y
Lake Namunamu	Grab sample	N
Lake Otamangakau	Phytoplankton net filter sample at lake outlet	N
Lake Duddings	Composite depth integrated grab sample	N
Lake Wiritoa	Composite depth integrated grab sample	N
Lake Pauri	Composite depth integrated grab sample	N

Last updated June 2018

 

FAQs

Where has Lindavia intermedia been found and what is being done about it?

Lindavia intermedia was discovered in Lake Waikaremoana in 2008, and is now known to be in Moawhango River. As the positive samples were taken 5kms and 40kms downstream of Lake Moawhango it is most likely to be present in the lake. Further investigation has indicated it is also present in Lake Rotoaira and Lake Taupō.

Horizons has undertaken testing at various freshwater lakes and popular fishing and recreational waterways within the upper reaches of our region. As results come in this page will be updated. While other waterways may also have Lindavia intermedia, rivers and streams with fast moving flows do not provide an ideal environment for the algae to thrive.

Councils are working with stakeholders and researchers to find out more about what conditions influence the growth of Lindavia intermedia. In particular, we are keen to understand what causes it to produce lake snow like it has in some South Island lakes.

How was it discovered?

Researchers were trying to figure out when lake snow first arrived in the country and were testing historic water samples.

Is Lindavia intermedia the same thing as lake snow?

Lindavia intermedia is a freshwater algae that poses no risk to food sourced from lakes where it is present or to human and animal health. Lindavia intermedia is an extremely small algae species that floats in water and has the potential to create lake snow. We haven’t seen or received reports of lake snow in lakes Moawhango, Rotoaira, Taupō, Rotokuru or Otamangakau, even though Lindavia intermedia is or could be present.

In the scientific world Lindavia intermedia is known as a diatom, meaning its cells are made out of silica. There are an estimated 100,000 different types of diatoms world-wide. With so many different species it isn’t possible for scientists to study them all in great detail. Lindavia intermedia is one of the less researched species, so we know comparably very little about it. Like all diatoms, Lindavia intermedia is microscopic. It’s smaller than the width of a human hair and it’s therefore difficult to detect its presence in lakes unless specific tests are carried out.

Lindavia intermedia is a plant and there are no human health risks. It is unlikely to affect the ecological health of lakes. Lindavia intermedia is thought to have come from North America.

So what’s lake snow? How would we spot it?

Lake snow is sticky and looks like strands of mucus or slime “hanging” under the water. Lake snow may be found by members of the public as slime on fishing gear and boat hulls. It could also cling to them when swimming. It can clog boat filters, as well as industrial and domestic water supply filters.

Is it just a matter of time before Lindavia intermedia produces lake snow in these central North Island lakes?

We simply don’t have the answer to that because researchers don’t know for sure what causes Lindavia intermedia to produce lake snow. What we do know is that it’s likely to have been in these lakes for more than a decade. Over that time, it has not produced lake snow and we have no evidence of it causing issues. 

How do we prevent the spread of Lindavia intermedia?

There is currently no known way of removing Lindavia intermedia or lake snow once it is present in a lake.
Our aim is to prevent the spread. NIWA research for lake snow presence in the South Island identified that methods used in Clean, Check, Dry are appropriate for use with lake snow.

You can help to protect your favourite waterways if you always check, clean, then dry any equipment that comes into contact with the water, between every waterway, every time.

Cleaning options are:

• Dishwashing detergent or nappy cleaner - 5% solution (500mls diluted to 10 litres in water). Soak or spray all surfaces for at least 1 minute, or
• Bleach - 2% solution (200mls diluted to 10 litres in water). Soak or spray all surfaces for at least 1 minute, or
• Freezing until solid.

Drying can be used as stand-alone treatment for non-absorbent items if you take great care to:

• Make sure gear is completely dry to touch, inside and out
• Leave dry for at least another 48 hours (after drying), before entering a different waterway.

Report anything that looks like lake snow to the Ministry for Primary Industry's hotline: 0800 80 99 66 and find out more about how to prevent the spread and ‘check, clean, and dry’ at www.mpi.govt.nz/check-clean-dry