Cyanobacteria found in Waituna Lagoon

Monitoring carried out by Environment Southland, on 15 August, has shown high abundance of planktonic cyanobacteria (blue-green algae) at Waituna Lagoon in Southland.

Planktonic (floating algae) cyanobacteria 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.

People and animals (in particular, dogs), should avoid contact with the lagoon, or be mindful of the potential health risks, until health warnings are removed.

Cyanobacteria occur naturally but can increase rapidly during warmer periods of the year.

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.

Environment Southland monitors cyanobacteria monthly at a number of river and lake sites across Southland, and the public will be advised of any changes in water quality that are of public health significance.

Find out more about cyanobacteria and our monitoring programme.

Read on to read answers to some frequently asked questions about cyanobacteria in general, and about the situation at Waituna Lagoon. Or you can download the FAQ document as a PDF file.

Frequently Asked Questions - Cyanobacteria

What is cyanobacteria?

Cyanobacteria (also known as blue-green algae, or commonly referred to as toxic algae), are an ancient group of photosynthetic bacteria (organisms that produce their own food using light).

There are two types of cyanobacteria – Benthic (rivers) and Planktonic (lakes). You are more likely to come in contact or notice benthic cyanobacteria as the mats detach from the riverbed, accumulating as scums along the river's edge or becoming exposed on the river's edge as the river level drops.

Cyanobacteria can produce toxins (called cyanotoxins) that are harmful to animals and humans when eaten, even licked, or when water containing the toxins is swallowed.

How do I know if cyanobacteria is present?

For rivers, it is not possible to inspect all reaches of river therefore you need to know how to identify cyanobacteria mats, and how to prevent yourself and your animals coming into contact with the potentially toxic cyanobacteria mats.

If the bed of a river is covered in thick dark brown or black mats that have a velvety texture and earthy/musty smell; it is better to be cautious and totally avoid that river site.

For lakes, even if no warnings are in place for a river, lake or bay, you should still assess the situation carefully before entering the water.

If the water of a lake is cloudy, discoloured, or has small globules suspended in it, it is better to be cautious and totally avoid that lake or bay.

Even if the water appears completely normal to the naked eye, it can still have large numbers of algae present.

How could I be exposed to cyanobacteria?

You could be exposed by recreating in a waterway with a cyanobacteria bloom, as your skin is likely to come in contact with the water, or you could ingest the water when doing things like water-skiing or swimming.

Not enough is known about when and why cyanobacteria are produced, so a precautionary approach is recommended: people, dogs and stock should avoid drinking river water in summer, and should avoid touching, licking or eating the cyanobacteria mats.

How can cyanobacteria affect me?

Many species of cyanobacteria produce natural toxins which can be poisonous to humans, dogs, livestock and wildlife. Exposure to high levels of these toxins may result in serious illness or death in both animals and humans. These toxins have no known antidotes. Children are at higher risk than adults for illness from cyanobacteria because they weigh less and can get a relatively larger dose of toxin. Often, the first sign that a cyanobacteria bloom exists is a sick dog that has been swimming in the area affected.

What should I do if I’ve been exposed and I’m feeling unwell?

Get medical treatment right away if you think you might have been affected by cyanobacteria. Contact your GP if you feel unwell or call Healthline on 0800 611 116 to talk to a Registered Nurse.

What should I do if I think my pets or livestock are affected?

Cyanobacteria can be particularly toxic to animals, especially dogs. If you think your pet or your livestock has been affected, contact your vet straight away.

Is it safe to drink water containing cyanobacteria?

No. Toxins are not removed by boiling, normal filter systems, or by adding household disinfectant.

How does cyanobacteria affect the environment?

Benthic cyanobacteria can form dense blooms of can block sunlight and use up all the oxygen in the water, killing other plants and animals.

Planktonic cyanobacteria may be invisible to the human eye, or it may cause the water to become cloudy. Advice is still being sought on the environmental impact of this type of cyanobacteria.

How can I protect myself, my family, and my pets from exposure to cyanobacteria?

  • Don’t swim, water-ski, or boat in areas where the water is discoloured or where you see foam, scum, or mats of algae on the water.
  • If you do swim in water that is contaminated with cyanobacteria, rinse off with fresh water as soon as possible
  • Don’t let pets or livestock swim in or drink from areas where you know there is an alert in place, or the water is discoloured, you see foam, scum, or mats of algae on the water
  • If pets (especially dogs) swim in contaminated water, rinse them off immediately—do not let them lick the algae or water off their fur
  • Respect any water-body closures announced by local public health authorities

How can I help reduce the occurrence of cyanobacteria?

  • Reduce nutrient loading of local ponds and lakes by using only the recommended amounts of fertilizers and pesticides on your yard
  • Properly maintain your household septic system
  • Maintain a buffer of natural vegetation around ponds and lakes to filter incoming water

Cyanobacteria and Waituna Lagoon

What may have caused it?
While cold temperatures in winter generally prevent them occurring, this cyanobacteria bloom is likely to be cause by a “perfect storm” type scenario, where many different things caused the right conditions for it to occur. Mild winter conditions, with high sun hours and low wind, lower than usual rainfall, higher levels of nutrients entering the waterways, and a sudden small increase in temperature are all things that could have triggered the bloom.

Has this happened before?

Yes this has happened before in Waituna, 29 October 2014. This event was a few months after the closing of the lagoon which triggered a build-up of nutrients.

Can this be expected from time to time?

Cyanobacteria blooms can occur naturally but high nutrient inputs tend to increase the number of and size.

What is the exact species?

The group of concern is called Picocyanobacteria.

How significant is this event in terms of preservation of the Waituna Lagoon in the long- term?

This type of event has occurred before and in isolation it should not be considered concerning in regard to the ecological health of the lagoon. However, Public Health concerns should be taken very seriously. If cyanobacteria appears more often, then it would be concerning for the lagoon’s health.

There are geese and swans on the lagoon that move from there to paddocks. Can they transfer the cyanobacteria to farm animals and potentially harm them?

As far as we know, cyanobacteria cannot be transferred from birds to paddocks resulting in the poisoning of farm animals.

Can the cyanobacteria be cleared by opening the lagoon to the sea to flush it?

Flushing may provide the clearing of some of the cyanobacteria, but will not provide a long-term solution.

Can I eat fish or shellfish from water with toxin-producing cyanobacteria?

Eating mussels and other shellfish from affected areas should be avoided as they can concentrate the cyanotoxins produced by the cyanobacteria. If you choose to eat fish from waters containing toxic cyanobacteria, you should eat them in moderation. Avoid eating the liver and kidney of the fish, as this is where accumulation of cyanotoxins may be the greatest. Fish may taste earthy. Avoid contact with the water while fishing and wash all fish in clean water.

Is it safe to boat or canoe in water with toxin-producing cyanobacteria?

How safe boating and canoeing are depends on the amount of direct contact with the water. If you swallow the water or your skin is in contact with the water while boating or canoeing, you are at risk from a reaction to any cyanobacteria that may be present. The higher the concentrations of cyanobacteria and the longer that people are in contact with the water, the more likely a reaction is to occur. Wash boats or canoes and life-jackets down with clean water after use.

Page reviewed: 30 Aug 2017 12:00am