Lake snow is­sue here to stay

Central Otago Mirror - - YOUR PAPER, YOUR PLACE - JO MCKEN­ZIE-MCLEAN

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.

❚ For the full story see Stuff.co.nz

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