A potentially toxic algae which appeared in Otago waterways
last month is disappearing, but has been replaced by another
potentially lethal algae.
The Otago Regional Council warned the public last month to
avoid Lake Waihola, Tomahawk lagoon and the Taieri River at
Henley because of the presence of the toxic blue-green algae,
which can produce toxins capable of
causing illness and irritation of the skin, eyes, nose and
Water samples at the locations this week confirmed that the
algae had dissipated, ORC resource science manager Matt
Hickey said yesterday. However, people using the three
locations now needed to be alert to the possible presence of
another potentially toxic algae called Phormidium.
''Unlike the blue green algae which has caused problems in
Lake Waihola and Tomahawk lagoon, Phormidium is found in
rivers and streams and typically forms a thick brown-black,
slimy algae mat found on large rocks, stones and cobbles,''
Mr Hickey said.
''If the mats detach, they may float downstream to become
caught up in other debris, such as sticks. When the
Phormidium mats die and dry out, they become light brown or
white. Either fresh or dried, the algae can be highly toxic
and potentially harm animals and people.''
Dogs were particularly susceptible to poisoning from the
algae, with symptoms including lethargy, muscle tremors, fast
breathing, twitching, paralysis and convulsions.
In extreme cases of animal poisoning, death could occur
within 30 minutes of symptoms appearing.
If people became ill, or suspected they had swallowed water
containing algal bloom, medical advice should be sought
immediately, Mr Hickey said.