Toxic algae still present in Waituna Lagoon

20 April 2018

Monitoring carried out by Environment Southland, on 16 and 23rd April shows there are still high levels of the toxic algae planktonic cyanobacteria in the Waituna Lagoon in Southland.

Planktonic cyanobacteria (floating or suspended algae) is different to that found in rivers during warmer months, but still produces toxins that can be harmful to people and animals if swallowed, or through contact with skin.

The most likely symptoms are skin rashes and blisters, but can include tummy pain and nausea. People would normally have symptoms within 12 hours of contact with the water.

If you experience health symptoms after contact with contaminated water, visit a doctor immediately. Animals that consume cyanobacteria should be taken to a vet immediately.

With duck shooting season approaching and more people in the lagoon area preparing maimais, people and animals (in particular, dogs), should avoid contact with the lagoon until health warnings are removed.

Environment Southland's freshwater and marine science leader Nick Ward said a number of lakes and lagoons are tested in the region every month for toxic algae as part of routine monitoring, but it isn't possible to find every bloom.

We can't be everywhere, so it's vital that people are aware that toxic algae can and will occur in our waters. While cyanobacteria found in rivers is easier to look for as it forms slime on rocks, the kind found in Waituna Lagoon is planktonic, the lake kind. While it can appear as greenish globules in the water, or a greenish tinge, in this case it's not visible and that's just the nature of this algae. Just because you can't see it doesn't mean it isn't there.

Public Health South health protection officer Sam Mangai said people consuming ducks shot and collected from the lagoon need to be aware of the health risks.

There is still much research to be done around cyanobacteria, and this is an area where we need more information. However, what we do know is there will be a level of risk to those who consume ducks or fish from waterways with toxic algal blooms.

Mr Mangai advises that consumption should be limited to less than one meal a week, and that the liver and other organs should be avoided, as this is where toxins accumulate in the duck's system.

Environment Southland monitors for toxic algae at various river and lake sites across Southland.

For further information, visit Environment Southland's website www.es.govt.nz.