Health Warning Lifted For Harmful Algal Bloom In South Bank Tributary Of The Waiau Uwha River At Waiau Bridge

Health New Zealand | Te Whatu Ora has lifted its harmful algal bloom health warning issued for the South Bank Tributary of the Waiau Uwha River at Waiau Bridge.

Recent cyanobacteria surveys of the South Bank Tributary of the Waiau Uwha River at Waiau Bridge has shown the cover of potentially toxic harmful algae (benthic cyanobacteria) has reduced and is now below levels that are of concern to public health.

Dr Imogen Evans, Public Health Medicine Specialist for the National Public Health Service, says Environment Canterbury’s monitoring of the South Bank Tributary of the Waiau Uwha River at Waiau Bridge will continue to the end of this summer and then will resume next summer when there is increased likelihood of cyanobacteria growth.

Facts about cyanobacteria:

· Cyanobacteria appears as dark brown or black mats attached to rocks along the riverbed.

· A low cover of the algae can occur naturally but can increase rapidly during warmer months. Algal blooms are influenced by a combination of available nutrients in the water and sediments (such as nitrogen and phosphorus), a sustained period of low and stable flows, and favourable weather conditions (for example increased temperature, calm days).

· It often has a strong musty smell and algal toxin concentrations can vary over short periods.

· 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.

· Pets that show signs of illness after coming into contact with algal mats should be taken to a vet immediately.

For further details visit:

https://www.lawa.org.nz/explore-data/canterbury-region

To contact your local National Public Health Service office visit: 
https://info.health.nz/locations/canterbury/national-public-health-service-canterbury-west-coast

To keep up to date with current health warnings visit: 
https://info.health.nz/health-alerts

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