Getting to the bottom of slime on lakes

Scientists are hoping to resume gathering slime known as ‘‘lake snow’’ from four Queenstown Lakes next week after their research was shut down by the Covid-19 crisis.

During the summer and autumn months for the past three years, Landcare Research principal investigator Phil Novis and University of Otago freshwater scientist Dr Marc Schallenberg have been monitoring and sampling lake snow on Lakes Wakatipu, Wanaka, Hayes and Moke Lake (7.5km northwest of Queenstown).

They are part of a team of nine scientists from research institutes around New Zealand working with Niwa on the collaborative Lake Snow Toolbox project.

The project seeks to determine the causes of the slime produced by the introduced algae Lindavia intermedia.

Dr Novis said this was to be their final year of testing the lake snow tools they had developed to generate data, but had only completed two out of nine tests on the lakes when the virus struck.

‘‘We had to go into a complete hiatus during the lockdown period. We had restrictions placed on field work and it is only recently that we have been allowed to do anything, so we are just trying to pick the ball up really.’’

Dr Novis said they had also planned to deploy a $10,000 1-metre wide doughnut shaped buoy specifically designed to monitor lake snow in Lake Wanaka’s Stevenson’s in March.

It was still sitting in a box in a laboratory at the University of Waikato.

‘‘It is an optical sensor that measures lake snow and sends the data to your desktop via the cellphone network every day, so you can be sitting in your office and see what the lake snow is doing right now in Stevenson’s Arm.’’

He said the buoy was no more accurate than their field testing but it would provide a far greater number of measurements.

They hoped to deploy it in August or September when the lake snow started to build up, with a peak usually in autumn.

He said the Ministry of Business, Innovation and Employment funded project had been given a six-month extension through to the end of March next year and results would follow soon after.

The lake snow tools would enable them to determine when the species produced the slime and how much, and to understand the biochemistry of the algae’s cells with a view to controlling the production of the slime, he said.


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