By Erica Mather 10/06/2016

Three iconic South Island lakes – Wanaka, Coleridge and Wakatipu, are being clogged with a particular type of algae that produces floating mucous or ‘lake snot’.

The alga called Cyclotella, or recently renamed by algologists as Lindavia intermedia, is related to the ‘rock snot’ alga didymo. The recent appearance of lake snot is associated with the emergence and dominance in Cyclotella, according to a team of scientists from the University of Otago, Landcare Research and Université Laval (Canada).

Lake snot is impacting on local water filtering systems, recreation and commercial fishing operations, particularly in Wanaka. Queenstown Lakes District Council are continuing investigations into a water treatment system to remove the slimy mucous.

Lake snow or snot

The unusual slime was first noticed accumulating on fishing lines and lures by people fishing in Lake Wanaka around 2004. In 2008, Tina Bayer identified the mucous while conducting experiments in the lake as part of her PhD. Her supervisor, Dr Marc Schallenberg from the University of Otago recognised it as the rare phenomenon called “lake snow” and linked it to abnormally high numbers of a new algae in the lake:

“I had studied over 100 lakes in Canada and New Zealand and had never seen lake snow before, but when we collected a routine sample of zooplankton from Lake Wanaka in 2008, I recognised the sticky flocs floating in the sample as lake snow, which had been reported in the scientific literature from only a few overseas lakes.

While scientists call the slimy flocs floating in the water ‘lake snow’, we think it looks more like lake ‘snot’.”

Why has Lake Wanaka become snotty?

Although Dr Schallenberg and colleagues have a number of hypotheses as to the sudden appearance of lake snot in 2004, the scientists have not settled on one single explanation. Over the past 20 years the Central Lakes region has grown steadily, with population growth and urban development among the most rapid in the country.

Local communities question whether environmental changes in the South Island’s lakes region and high country may be related to the establishment of this nuisance organism.

Amy Weaver, also a PhD student supervised by Dr Schallenberg, has investigated the effect of intensifying farming and fertiliser use in the catchment surrounding the lakes. Her research shows that even small amounts of rural land use intensification can have marked impacts on the movement of nitrogen and organic matter from the land to the lake.

PhD student, Tina Bayer has studied the conditions that are important for algae in the lake and has found evidence that suggests climate change is having a subtle effect on these conditions.  Dr Schallenberg comments on how Cyclotella affects the ecosystem of the lake:

“These flocs become sticky ‘hotspots’ of biological activity, floating in the very clear and clean lake waters. While they are a nuisance to people using the lake, their presence in the lake also undoubtedly changes the way the lake ecosystem functions.”

Snotty lakes

Scientists hope to identify where the algae originated from and how it is being transmitted between lakes. They also plan to study why it has inundated lakes only recently and the reasons for its enormous secretion of slime. However, funding for these research projects has not yet become available. Dr Schallenberg says:

“I’m not sure if this reflects the general low levels of investment in science in New Zealand or that there is a reticence by governments to support research into emerging environmental problems for fear that our reputation as ‘clean-green’ country will be tarnished.”

However, Dr Schallenberg emphasises how supportive the local Wanaka community has been:

“The local people understand the importance of Cyclotella and lake snot, not just to them and their lake, but to the bigger picture of New Zealand’s changing environment. When this unpleasant material stops you fishing, sticks to you when you’re swimming and clogs the water filters on your washing machine, dishwasher and sprinkler, you get the picture pretty quickly.

This has important implications not only for the environment and the economy but also for our well-being and sense of connection to the environment.”


Featured image: Lake Wanaka, CC flickr unkle_sam

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0 Responses to “Southern NZ lakes congested with algal snot”

  • Is this snot easily transferable like didymo? So risk of spread around NZ or is it already present in other lakes ie Taupo?

    • Hi Brenda,
      Both Cyclotella and didymo are members of a group of algae known as diatoms that can secrete large amounts of mucous, or polysaccharide under certain environmental conditions.

      “There [is] an obvious similarity to the invasion of relatively unpolluted South Island rivers by the nuisance algae, Didymosphenia geminata (didymo, also known as “rock snot”), in around 2004,” says Dr Schallenberg.

      According to research, prior to discovering Cyclotella in Lake Wanaka in 2004, the organism was found in two other South Island lakes (Aviemore and Hayes) but in relatively low numbers. Although present, Cyclotella was not producing lake snot in these other lakes. Cyclotella found a more preferable habitat in Lake Wanaka where it produces lake snot.

      Unfortunately, barriers to research have meant little is known about how Cyclotella is transferred from lake to lake. Scientists are eager to learn which lakes are at risk from further invasions of lake snot, what factors promote or limit its formation and what could be done to prevent or slow its spread.

      • My concern would be that it is transferable like Didymo is … but do we know what would kill this algae – just the 5% detergent as per Didymo or would we require something else. Hopefully this info would be available fairly quickly.
        Ie – Freshwater user moves from one Lake to another Lake before gear has dried out so uses the 5% detergent mix for Didymo, but this does not kill Lake Snot …..