Algal bloom at Te Awanga. Photo supplied.

As the summer sun beats down on us in Hawke’s Bay, and people start heading towards a water body to cool down, Te Whatu Ora advises caution be taken if it looks bad, smells bad, has green or brown particles suspended in it or if scum or leathery mats of algae are on the surface or the bottom of the waterway.

Three HB sites are unsuitable for swimming – Esk River due to Cyclone Gabrielle damage, Clive River, which is generally not suitable for swimming, and Waipuka Stream.

Hawke’s Bay Regional Council also advised caution around Te Awanga Beach due to the appearance of abright, rust coloured algal bloom along the shoreline near Te Awanga and Haumoana.

HBRC’s Environmental Information Team took samples on December 21 to determine if the algal bloom is toxic.

Regional Council senior scientist marine and coasts Becky Shanahan said algal blooms were common in Hawke’s Bay after periods of heavy rain and warm temperatures when conditions are just right for algae to grow.
“Most algal blooms are harmless and are a food source for marine life. Only around two percent of algal species can produce toxins that can harm marine life. While they typically don’t cause issues for people, they can in rare cases,” Shanahan said.

“Our teams will continue monitoring the bloom as the composition can naturally change over time. If results change and indicate levels of high risk for the community, Te Whatu Ora will be notified, and further guidance will be provided.”

Te Whatu Ora Medical Officer of Health for Toi Te Ora Public Health Gregory Evans said algal blooms had the capacity to release toxins into the water which can cause skin rashes, stomach upsets and visual problems for anyone who has contact with the water.

“They can also affect the nervous system causing numbness, difficulty with breathing, and asthma attacks,” Evans said.

Lakes are typically dominated by free-floating algal blooms, while rivers are more prone to algal blooms that grow in mats attached to rocks at the bottom.

They can also build up at the shoreline.

“Algal mats and scum can build up along the edges of lakes or rivers. It’s important parents ensure children avoid contact with these as they may be toxic,” he said.

The public health advice: If you think you’ve been in contact with an algal bloom, shower and change your clothes as soon as you are able to, even if you don’t have any symptoms. You should seek medical advice from your GP if you become unwell after having contact with recreational water.

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