Rain flushes toxic algae from rivers

High river flows as a result of prolonged rainfall during Monday and Tuesday appear to have largely cleared toxic algal mats from the Hutt River.

Greater Wellington environmental scientist Summer Warr said that inspection of popular bathing sites along the Hutt River today had showed that the thick blue-green algal mats on banks and shallow areas in some parts of the river appear to have been largely flushed away. Three dog deaths last week have been attributed to toxins produced by these algal mats.

High river flows are also likely to have flushed algal growth from the Wainuiomata, Waikanae and Otaki rivers. Blue-green algae may remain in streams and rivers not affected by high flows.

However, Ms Warr warns that the return of warm stable weather will bring renewed blue-green algal growth within a few weeks. "It is a good idea for all river users to have a really good look at any river spot before they swim, wade, paddle or allow their dogs to have contact with the water, regardless of whether warning signs are in place or not". River users and their animals should avoid contact with dark brown or black algae mats which grow attached to rocks in the river bed or accumulate on the surface in shallow, slow flowing areas. The algae often give off a strong musty smell.

Dogs are particularly susceptible to poisoning from blue green algae as they like to scavenge and drink along river edges. Humans can also be affected by blue green algae toxins.

Given the likelihood of algal mats returning again this summer, Regional Public Health and local council staff have advised precautionary warning signs will remain along the Hutt, Wainuiomata and Waikanae Rivers to remind rivers users of the potential risk until further notice.

ENDS

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