March 14, 2026

#regional: Health Warning Lifted After Algal Bloom at Te Roto o Wairewa

Matthew Tukaki Posted On March 14, 2026

Health authorities have lifted a public health warning for Te Roto o Wairewa, also known as Lake Forsyth, after recent monitoring confirmed the harmful algal bloom that prompted the advisory has subsided.

Health New Zealand says water testing now shows toxin levels have dropped to a point where the lake no longer poses the same level of risk to people, pets and livestock. The warning had been issued earlier after potentially toxic blue-green algae, known as cyanobacteria, was detected forming surface scum on the lake.

During the alert, the public had been advised to avoid contact with the water, including swimming, wading or letting animals enter the lake, due to the risk of exposure to toxins produced by the algae. Cyanobacteria can cause symptoms such as skin irritation, nausea, stomach cramps and other health effects if people or animals come into contact with contaminated water.

Officials say conditions at the lake have improved following ongoing monitoring, allowing the advisory to be removed. However, authorities are continuing to test the water and warn that algal blooms can re-emerge quickly, particularly during warm weather or when water conditions favour their growth.

Te Roto o Wairewa is located near Little River on Banks Peninsula in Canterbury and is a shallow coastal lake connected to the sea through a gravel bar at Birdlings Flat. The lake has periodically experienced algal blooms due to a combination of warm temperatures, nutrient runoff and low water movement.

Health officials say people visiting the lake should still exercise caution and remain alert for signs of algal growth, such as discoloured water, floating scum or strong odours. If these signs appear, people and animals are advised to avoid contact with the water and report concerns to local authorities.

Monitoring of Te Roto o Wairewa will continue as part of routine water quality checks to ensure the lake remains safe for recreational use.

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