Watch for toxic algae in rivers and streams

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Watch for toxic algae in rivers and streams

Toxic algae is starting to appear in some Marlborough streams and rivers. Parents and dog owners are warned that it poses a health risk to children and animals.

Higher concentrations of the algae are present in parts of the Omaka and Wairau rivers. While Council has placed warning signs at some of the access points, please note that the algae could be present in other areas, not just those signposted. If a river bed is covered in thick brown or black mats that have a velvety texture and an earthy or musty smell, please avoid that area.

The toxins in the algae have the greatest effect on dogs, which are attracted to the smell and can die after eating it. Even a small amount can be fatal to a dog when ingested. The neural toxins produced by the algae cause muscular twitching, paralysis and convulsion. If your dog shows any of these symptoms after spending time in a river, take it to the vet immediately. While there have been no reports of dog deaths in Marlborough, there have been some in Nelson-Tasman.

In humans, contact with toxic algae can cause vomiting, diarrhoea and skin irritation. Keep children away from the algae; avoid touching it or swimming near it.

Toxic algae are naturally occurring. They are more prolific in summer when longer days and higher temperatures provide good growing conditions. The warmer weather and lack of floods to flush the rivers seems to have prompted an early bloom. Algal mats may be floating at the river's edge or in shallow water or attached to rocks in fast-flowing parts of a river.

More information on toxic algae