Blue-Green Algae Red Alert for Mannus Lake – June 2024

Published on 24 June 2024

Mannus Lake Algae Warning Sign.jpg

Council has issued a blue-green algae Red Alert for Mannus Lake and warning signs are in effect at key recreational areas around the lake.

Red alert levels represent 'bloom' conditions. The water may appear green and may have strong, musty or organically polluted odours. Blue-green algae may be visible as clumps or as scums.

The 'blooms' should be considered to be toxic to humans and animals, and the water should not be used for drinking (without prior treatment), stock watering, or for recreation.

As per the Regional Algae Contingency Plan people are reminded not to enter the water, not to drink untreated water or bathe in water drawn from the lake or creek while the red alert level warning is in place.

Livestock owners should monitor stock water supplies and remove stock from waters where surface scum is visible or blue-green algae is suspected.

A red alert level warning indicates that people should not undertake recreational activities where they may be coming into direct contact with the water. Contact with the water may also pose a threat to livestock, and pets. 

People should not eat mussels or crayfish from Red Alert warning areas. A precautionary approach should be applied to fishing during bloom events.

Any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of before consumption. Fish fillet meals from algal bloom affected areas should be limited to 1-2 servings per week.

Avoiding fishing in a bloom location is the best way to minimise risk, particularly catching and eating fish from locations with severe blooms that last extended periods of time.

Council has increased water sampling at the lake and downstream to a weekly monitoring frequency and the Red Alert will be lifted when two consecutive samples fall below the high alert.

Blue-green algae occurs naturally at low levels in lakes and rivers, however they may reproduce quickly in favourable conditions where there is still or slow-flowing water, abundant sunlight and available nutrients.

People who believe they may have been affected by blue-green algae are advised to seek medical advice.

Information updates about blue-green algae blooms and red level warning areas can be obtained from