Environment Canterbury warns a toxic algae suspected of
having caused the death of a dog last summer could be
reoccurring in some rivers after recent warm, dry weather.
Environment Canterbury (ECan) field staff have noticed algal
mats, likely to be phormidium, in South Canterbury's Pareora
River and downstream reaches of the Opihi River, as well as
North Canterbury's Ashley River, in recent days.
People living at Pareora huts have been spoken to by ECan
staff.
ECan water-quality analyst for South and Mid-Canterbury,
Graeme Clarke, said this year, following new Ministry for the
Environment guidelines, there would be additional freshwater
monitoring for phormidium.
Last summer, the toxic algae was linked with the death of a
dog at the Ashley River.
Dogs at the Selwyn River were also reported to have become
seriously ill through licking the blackish-brown algal mats
on river rocks.
Staff taking freshwater samples as part of the summer
swimming water-quality programme will be keeping an eye out
for algal mats.
If mats are present, samples may be sent to the Cawthron
Institute in Nelson for toxicity testing.
Dog owners should keep their animals on a leash in any areas
where they can see the blackish-brown algal mats and report
any sightings and locations to ECan in Timaru or
Christchurch, he said.
Phormidium is a naturally occurring, freshwater, brown-black
algae.
Although district or city councils may put up warning signs,
these may not be seen at the many river-access points, hence
the need for people to treat every low-flowing river with
caution.
The algae forms dense dark brown-black mats on river stones.
When the mats break away, particularly after a downpour, they
accumulate at the river's edge.
Contact with the skin or through swallowing can cause rashes,
skin and eye irritation, allergic reactions, gastrointestinal
upset and other effects in humans.
Fishermen and boat users should also exercise caution.
In the case of illness or suspected illness, advice should be
sought from a doctor or veterinarian.
david.bruce@odt.co.nz
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