Lakes study to search for answers

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Trophic studies on Lakes Wanaka, Hawea and Wakatipu are about to begin, with the Otago Regional Council (ORC) hoping the sampling will throw new light on the problematic lake snow.
Lake snow (also known more recently as lake snot) is thought to caused by the algae Cyclotella bodanica and has been found in Lake Wanaka since 2004.
In May it was also found in Lake Wakatipu and this month a fisherman reported finding a similar slime in Lake Hawea.
A report by regional council freshwater resource scientist Adam Uytendaal said University of Otago limnologist Marc Schallenberg found lake snow in Lake Dunstan in February last year.
‘It is hypothesised that it was likely washed downstream from Lake Wanaka,’’ Mr Uytendaal’s report says.
During this month’s sampling programme, information would be collected that would help ‘‘experts’’ better understand the southern lakes and the algae known to be responsible for fouling fishing gear, blocking boat intake filters and household domestic appliances including drinking water filters, washing machines and sprinklers.
Sampling was last done in 2006 and 2009.
Concern about the health of southern lakes and the lack of a co-ordinated management plan has become a talking point at local body election meetings, with some Wanaka candidates saying they support the establishment of a freshwater resource centre.
The guardians of Lake Wanaka have also called for a lake management plan encompassing Lakes Wanaka, Hawea and Wakatipu.
However the regional council report said at present there was no ‘‘definitive management options’’ and that further research was needed to understand why lake snow was present in three lakes.
Further research could include DNA analysis of the algae in New Zealand and overseas as well as lake sediment analysis.
Although the floating mucous associated with lake snow was non-toxic and posed no risk to human health it could pose ‘‘significant biosecurity implications’’ to Otago and elsewhere in New Zealand if it was identified as an invasive species, Mr Uytendaal said in his report.
Its spread in Lakes Wanaka and Wakatipu had economic implications in terms of domestic and industrial water supplies as well as on recreation and tourism.
The council planned to approach Biosecurity New Zealand to ‘‘discuss the possibility’’ the algae was an invasive species, he said.
ORC director of engineering, hazards and science Gavin Palmer told The Newsthe sampling programme would begin on Tuesday.
‘‘It is a measure of the level of ‘enrichment’ of [the] lake recommended by the Ministry of the Environment as a useful tool for measuring lake trophic status in New Zealand,’’ Dr Palmer said in an email.
He doubted the algae would establish itself in Lake Dunstan.
‘‘Lake snow has been present in Lake Wanaka since 2004 and Lake Wanaka discharges directly into Lake Dunstan. If Cyclotella was going to establish itself in Dunstan and produce lake snow, itwould have done so by now.’’
Provisions covering rural discharges to water were already covered in the Otago Water Plan and the council was also working on the development of a strategy to help minimise the effect of contaminant discharges from stormwater, septic tanks and industrial wastewater.