Lake algae found in Waikato and Manawatū-Whanganui regions for first time
Lindavia intermedia, a microscopic freshwater algae species, has been found in the Waikato and Manawatū-Whanganui regions for the first time. Its discovery prompts a reminder to all water users to ‘check, clean, and dry’ when moving between waterways.
Lindavia intermedia is an extremely small freshwater algae species that floats in the water column of lakes and has the potential to create lake snow. It poses no risk to food sourced from lakes or to human and animal health. Currently there is no known impact on the health of lakes, however further research is needed.
Lindavia intermedia was discovered in the North Island in Lake Waikaremoana in 2008. Early this year, researchers from NIWA were trying to figure out when lake snow first arrived in the country and tested historic water samples. They confirmed with Horizons Regional Council late last month that Lindavia intermedia was present in samples taken from the Moawhango River. While the positive samples were taken 5kms and 40kms downstream of Lake Moawhango, it is most likely to be present in the lake.
Following conversations with Waikato Regional Council, iwi, and other stakeholders, further investigation has indicated it is also present in Lake Rotoaira and Lake Taupō. Meanwhile, testing is underway on water samples collected from lakes downstream from Lake Taupō.
Horizons Regional Council’s samples from Lake Otamangakau have come back clear, however the council will undertake additional testing at popular fishing and recreational waterways such as Lakes Wiritoa, Dudding and Namunamu.
Horizons freshwater scientist Michael Patterson says that where Lindavia intermedia has been found it’s likely this algae species has been in these lakes for more than a decade. This is because the historic samples recently retested are from as far back as 2005.
“Over that time, the Lindavia intermedia has not produced lake snow effects as far as we are aware and we have no evidence of it causing issues to lake users,” says Mr Patterson.
“There is currently no known way of removing Lindavia intermedia once it is present in a lake or waterway. The conditions necessary to produce the lake snow effect are not clear, more research is needed.”
“As lake snow produces mucus-like strands of slime which hang and drift under the water, sticking to fishing gear, boat hulls, swimmers, and can clog boat, industrial and domestic water supply filters, we’re keen to prevent it,” says Waikato Regional Council biosecurity officer Paul Quinn.
“Water users play a critical part in protecting their favourite waterways,” says Mr Quinn.
“The key is to always check, clean, then dry any equipment that comes into contact with the water, between every waterway, every time.”
While other waterways may also have Lindavia intermedia, rivers and streams with fast moving flows are believed to be less than ideal environments for the algae to thrive.
Both regional councils are looking at options for adding Lindavia intermedia testing to their regular monitoring programmes and are working with stakeholders and researchers to find out more about what conditions influence the growth of the algae.
“In particular, we are keen to understand what causes it to produce lake snow like it has in some South Island lakes,” said Mr Quinn.
NIWA research for lake snow presence in the South Island identified that the Check, Clean and Dry methods used for didymo are also appropriate for use with Lindavia intermedia and lake snow.
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.
To find out more on how to protect our waterways, visit www.mpi.govt.nz/check-clean-dry.