Be alert for toxic algal blooms

Holiday makers are being reminded to be on alert for toxic algal (cyanobacteria) blooms this summer.

Blooms of cyanobacteria are a health risk and can cause irritation of the skin, eyes, nose and mouth on contact with water or inhaling droplets and are particularly harmful to dogs.

Dr Ramon Pink says it is the time of year when toxic algal blooms can proliferate in our recreational water ways.

"Environment Canterbury frequently monitors popular swimming sites but not all recreational waterways can be observed, so people need to look out themselves for these blooms whenever they go near any waterway – whether that is a river or a lake," Dr Pink says.

If ingested toxins can create symptoms such as vomiting, diarrhoea, cramps, nausea, muscle tremors, fast breathing, twitching, paralysis and convulsions.

"Children and dogs are very susceptible to toxin exposure because they may ingest or play with the mats," he says.

Dr Pink urges anyone experiencing a serious reaction with any of these symptoms, who may have been in contact with cyanobacteria, to seek medical attention urgently.

"If you, your child or your pet has come into contact with these mats, seek medical or veterinarian advice as soon as possible."

In rivers the cyanobacteria is usually in a 'benthic' form. It grows on rocks and stones on the bottom of the river, forming a dense brown, green, black or purple growth, which can become detached and accumulate along edges of rivers.  These mats can contain toxins which are harmful to both people and dogs.

When conditions are favourable in lakes the cyanobacteria cells can multiply and form blooms, sometimes accumulating in bays and shallow areas as a green scum.

The latest health warnings for water ways can be found:!/EnvironmentCanterbury?fref=ts

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Page last reviewed: 20 December 2013