Waituna update: Toxic algae alert removed for lagoon
The alert for potentially toxic algae at the Waituna Lagoon has now been removed after monitoring carried out by
Environment Southland this month showed reduced levels of planktonic cyanobacteria (floating or suspended algae) in the
Waituna Lagoon. The alert had been in place since March 29 this year. Planktonic cyanobacteria can produce toxins that
can be harmful to people and animals if swallowed, or through contact with skin.
On May 30 the Waituna Lagoon was mechanically opened to the sea after water levels exceeded the 2-metre trigger level.
The decision was made as these levels were affecting surrounding farmland, and further heavy rain was forecast.
Environment Southland’s freshwater and marine science leader Nick Ward said today that while the lagoon opening had a
flushing effect on the toxic algae, as expected, toxic algae were still present at low levels, which could increase
“Environment Southland monitors potentially toxic algae monthly at a number of river and lake sites across Southland,
but it’s important the public are aware that toxic algae can occur in our waterways at any time. It’s about knowing what
to look out for when you are out and about, as well as keeping an eye on our toxic algae alerts”.
Toxic algae in rivers can appear as a brownish black slime on rocks, or black mats, which can also move downstream into
lakes. This type of toxic algae (benthic) can also form in lakes, or as in the case of Waituna, the planktonic kind may
be present, and can appear as a greenish tinge, green globules, or be invisible to the naked eye.
If you experience health symptoms after contact with contaminated water, visit a doctor immediately. Animals that
consume toxic algae should be taken to a vet immediately.
Toxic algae alerts can be found at Environment Southland’s website www.es.govt.nz