Lake snow issue here to stay
Lake snow - there is no way to get rid of it, the job now is not to spread it, an Otago University scientist warns.
University of Otago freshwater scientist Dr Marc Schallenberg delivered a talk on Wednesday in Queenstown hosted by Catalyst Trust on the nuisance algae, Lindavia (formerly known as Cyclotella) and its sticky product - lake snow.
The algae is a slimy, sticky organism now found in Otago Lakes Wanaka, Wakatipu, Hawea, Dunstan, as well as Lake Coleridge in Canterbury. The algae is a nuisance for recreational lake users, as well as clogging filters in Queenstown and Wanaka’s water supply.
Schallenberg said the recent spread of the algae could pose a national problem, as it could spread to lakes around the country.
‘‘There is no way you get can rid of it...It will probably spread naturally but people should try not to encourage its spread.’’
There was hope the lake snow would ‘‘disappear’’ again, as it had in Lake Benmore and Lake Waikaremoana which were also nutrient-poor lakes, similar in nature to the Otago lakes, he said.
‘‘We don’t know why it has disappeared from some lakes. It is really understudied. We have some hypotheses about why it suddenly showed up and started producing its slime, but so far we haven’t succeeded in getting funding to test our ideas.’’
Schallenberg’s colleague, Phil Novis, from Landcare Research, is currently studying its genetics to test if it is an exotic invasive species, or a species that was at home here and is suddenly growing in response to an environmental change.
‘‘If the latter, then maybe the factor causing it to bloom could be controlled (like the amount of nutrient coming into the lake), or maybe the driver is something we can’t control (like climate warming). Unless we study it, we just won’t know.’’
For the moment, Schallenberg suggested lake users treat boats and equipment the same as didymo to prevent its spread. It could, however, be more difficult to remove than didymo because of its greater stickiness.
A research proposal is being put together to develop technologies to sample and monitor lake snow, including sensors or equipment lowered down into lake that would give instantaneous readings.
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