The Otago Regional Council yesterday confirmed the Arrow
River has tested positive for didymo.
In March the Otago Daily Times reported a sample taken
from the irrigation scheme at The Hills had tested positive,
prompting the ORC to test the Arrow River, which had
previously been clear.
Although surrounding rivers, including the Motatapu, Shotover
and Kawarau, were infected with the micro-organism, also
known as rock snot, it had been hoped the spread into the
Arrow could be stopped.
However, ORC environmental monitoring director Jeff Donaldson
said yesterday attempts to prevent the organism's spread into
the Arrow were unsuccessful.
''It's disappointing but it probably wasn't unexpected.
There's a lot of recreational activity in that area,
particularly over summer months.
''It was a river that was probably a little bit harder to
identify it in ...
''People won't recognise it in your waterways ... you have
that high sediment movement ... you will never find biomass
Signs were already in place around the river to educate users
on didymo and how to prevent its spread and Mr Donaldson said
they would stay.
''We don't put up signs to say 'This waterway is affected'
... We want people to change their behaviours on every
Despite a large number of rivers and lakes in the wider Otago
area being affected, the focus remained on those which were
still ''pristine'', including the Taieri River and lakes
including the Poolburn, Manorburn and the Blue Lake.