MEDIA RELEASE
December 21, 2012
Otago Public Reminded About Toxic Algal Blooms
The Otago Regional Council (ORC) and Public Health South are reminding the public to keep their distance from some
popular swimming locations in Otago because of potentially toxic algal blooms. The two organisations have reiterated
their earlier warning of December 6 for people not to come in contact with the water in these places.
ORC director of environmental information and science John Threlfall said it has been confirmed that Lake Waihola south
of Dunedin, the upper Tomahawk lagoon, and the lower Taieri River near Henley, contain the potentially toxic blue-green
algae Anabaena lemmermannii. However, it could be present in other areas as well.
This algae, which is dark green, can produce a series of toxins which are then passed to the water and can be fatal to
dogs and cause illness in people. The degree of toxicity is impossible to predict, but a test carried out on a sample
from Lake Waihola showed that no toxins were present at that time at that point.
Southern District Health Board Medical Officer of Health Dr Marion Poore said people swimming in water with increased
levels of algal bloom have been known to develop allergic reactions: asthma, eye irritations, rashes, blistering around
the mouth and nose, and gastro-intestinal disorders, including abdominal pain, cramps, and diarrhoea.
People should not swim in areas affected by the algae, and other water users, including fishermen and boat users, should
exercise caution, Dr Poore said.
Any reaction depends on the type of toxins present, and the concentration of the toxin in the water. The higher the
concentration of toxins and the longer the contact with the water, the more severe the symptoms are likely to be. It is
difficult to know whether toxins are present at any one time or location, therefore a precautionary approach is strongly
recommended.
Dogs are particularly susceptible to poisoning from both mat-forming and free-floating toxic algae as they enjoy being
in the water and can consume these algae intentionally or by accident. Livestock are also at risk from poisoning from
cytotoxins and should be provided with alternative drinking water.
Symptoms of poisoning in animals exposed to the type of toxins present in anabaena mats include lethargy, muscle
tremors, fast breathing, twitching, paralysis, convulsions. In extreme cases, death can occur within 30 minutes after
signs first appear.
“In the case of illness or suspected illness after swallowing water containing algal bloom, seek advice from your
doctor. If your animals become sick, contact your veterinarian immediately," Dr Poore said.
ORC has put out warning signs at the locations where the algae has been found, but not all sites will be known.
Dr Poore says her office has received a number of calls from the public concerned about the safety of eating fish caught
in these waters.
“Unfortunately, there is very little information about the potential toxic effects of eating fish caught from waters
with a cyanobacteria bloom,” she said.
Some algae toxins have been found to accumulate in fish tissues, especially in the internal organs such as the liver and
kidneys. Toxin accumulation studies suggest that the muscle (fillet) tissue is less affected by algae toxins.
Dr Poore said people choosing to eat fish caught from waters affected by a blue-green algae bloom should use gloves when
removing the fat, skin, and organs before cooking, and be careful not to cut into the organs.
Before cooking or freezing the fish, the fillets should be rinsed with clean water to remove any contaminants from the
cleaning process.
It is also important to wash all equipment in clean water afterwards.
“As a precaution, we advise against eating any freshwater shellfish such as kakahi or freshwater mussels,” Dr Poore
said.
“For those people who eat a lot of fish taken from cyanobacteria bloom-affected waters there is a potential risk of
accumulation of toxins in their system. Limiting the number of fish meals to two per week will help avoid this
situation,” she said.
ENDS