Lindavia is a ‘clean water’ alga
Lake snot abounds. Is Wanaka’s water clean or dirty? Recently while chatting with people down at the lake I’ve become aware of an attitude that lake snot is thriving in Lake Wanaka because it is experiencing an increase in plant nutrients (nitrogen and phosphorus).
The opposite may be the case. Lindavia is a ‘clean water’ alga but has flourished in its new home. It is an invisible singlecelled diatom that lives with other algae in a layer beneath the surface. But when it multiplies, its silicon walls latch onto neighbouring cells and clumps become visible as lake snow.
In 2008, when I was helping a PhD student sample water in
Roys Bay, we located the layer of lake snow and that’s exactly what it looked like – a snow storm.
According to Professor David Hamilton, New Zealand’s leading lake ecologist, it is possible that exploding Lindavia use up the meagre supplies of phosphorus and nitrogen in the water but must get rid of carbon – by leaking it out.
The carbon could be an energy source for bacteria that colonise the lake snow – converting it into the much-loathed lake snot. And the lake snot is what has been blocking filters and coating Lake Wanaka swimmers, especially this past summer.
The combination of Lindavia cells, bacteria and associated mucus hangs in amber coloured strings in the water column. During the Ruby Swim one guy told me he thought it was his hair swirling in front of his eyes – but it turned out to be threads of lake snot. Swimmers emerged with their faces covered in an unsightly film of these threads. I understand swimmers who don’t shower immediately begin to stink within an hour or so!
The mucus associated with lake snot blocks filters such as those installed in town water supply intakes, washing machines, dishwashers and garden sprinklers. If not cleaned, the mucus sets like concrete and the filters must be replaced.
ORC is researching Lindavia’s origins so we’ll know the kinds of lake conditions it ‘‘normally’’ inhabits and whether it morphs elsewhere into lake snot. And tapping into alternative town water supplies, such as Cardrona water, is a possibility QLDC will no doubt be considering.
As for a ‘magic’ cure? Like its river equivalent, Didymo (also a clean water diatom), that’s unlikely. But seasonal and annual variations in climate and other factors are likely to see lake snot come and go and some years it may cause no issues at all.
The fundamental lesson though, with all organisms that are inadvertently or otherwise brought into our country, is that our ecology is not adapted to these organisms and has no natural defenses against their unfortunate impacts. And that is why biosecurity is becoming one of the foremost issues facing Aotearoa.
❚ Laurel Teirney is an aquatic scientist, facilitator and writer.