Red algal blooms in Waikato River hydro lakes

The latest test results from lakes Karāpiro, Maraetai and Arapuni show higher than normal concentrations of a red algae.

The tests follow reports of reddish-brown areas of water at these lakes, which Waikato Regional Council scientists have confirmed as algal blooms.

While the algae do not produce harmful toxins, people should take extra caution as it can irritate your skin and respiratory system.

Pet owners should keep their animals away from any discoloured water, especially dogs, which may be attracted to its odour.

Dr Mafalda Baptista, senior water scientist at Waikato Regional Council, explains that algae can often “bloom” in waterways during hot summer conditions like we have experienced in recent weeks, as the conditions in the hydro lakes (available nutrients, slow flow) are suitable for algae to thrive in. 

“A bloom occurs when an algae population grows rapidly, which visibly discolours the water.”

The test results showed the algae are a dinoflagellate species. This is not the first time the Waikato River has experienced blooms of this red algae. In early 2015 a similar event took place, and this algae is commonly present in the Waikato River.

“That doesn’t mean you can’t swim anywhere in the lakes but check the water for signs of algae and stay away from it.”

The council also encourages people to check its latest test results at LAWA.org.nz ‘Can I swim here?’