Algal bloom results in health warnings at Lake Ellesmere and Whitecliffs Domain

Friday January 25, 2013

The Community and Public Health division of the Canterbury District Health Board have issued health warnings after potentially toxic blue-green algae were found in the Selwyn River at the Whitecliffs Domain and in Lake Ellesmere / Te Waihora.
 
The algae can produce toxins harmful to people and animals.
 
Dr Alistair Humphrey, Canterbury medical officer of health, says that people should stay out of the water at both of these places until the health warnings have been lifted.
 
“Contact with the algae may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips,” Dr Humphrey says.
 
“If you experience any of these symptoms visit your doctor immediately and let your doctor know if you have potentially had contact with the algae.
 
“People should not drink water from the Selwyn River at the Whitecliffs Domain or Lake Ellesmere / Te Waihora at any time. Importantly, boiling water does not remove the toxins”.
 
He says that the algae are particularly dangerous for dogs.
 
“Dogs should be kept away from both places until the health warning has been lifted. Animals that show signs of illness after coming into contact with the water should be taken to a vet immediately”.
 
Environment Canterbury is monitoring the sites and the public will be advised of any changes in water quality.
 
Selwyn River Whitecliffs Domain
The potentially toxic blue-green algae (benthic cyanobacteria) has been found in the Selwyn River at the Whitecliffs Domain. The algae look like dark brown to black mats.
 
Reticulated town water supplies are currently safe but no one should drink the water from the river at any time.
 
Lake Ellesmere / Te Waihora
Increased concentrations of blue-green algae (planktonic cyanobacteria) have been found in Lake Ellesmere / Te Waihora.
 
The algal bloom is predominantly comprised of picocyanobacteria which have been found to produce toxins in studies around the world. 
 
The mechanisms of toxicity are very diverse, ranging from rapid onset of nausea and diarrhoea, to gastroenteritis and other effects such as tingling and numbness around the mouth and fingertips, liver damage.
 
Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and liver and wash in clean water.
 
Anabaena and Nodularia are the usual cyanobacteria species found in Canterbury lake algal blooms that have led to health warnings in the past and these species are not currently being detected in lake samples.
 
Facts about cyanobacteria:
  • Appears as dark brown/black mats attached to rocks along the riverbed.
  • The algae occur naturally but can increase rapidly during warmer months.
  • It often has a strong musty smell and algal toxin concentrations can vary over short periods with changing environmental conditions.
  • Although high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins.
  • If a health warning is in place avoid contact with the water.
  • Although district or city councils may place warning signs, these may not be seen at the numerous river access points, hence the need for people/ dog-walkers to treat every low-flowing river cautiously.
Or contact Community and Public Health on (03) 364 1777.
 
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Page last reviewed: 09 July 2013
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