SA Health has issued a warning to avoid drinking water from Lake Alexandrina and to avoid body contact through swimming and diving until further notice. The main area affected is the Goolwa Channel from the Barrage to Point Sturt near Clayton Bay.
Water samples collected on 2 May 2025 from Lake Alexandrina showed elevated levels of potentially harmful freshwater blue green algae Cylindrospermopsis across the lake.
The Cylindrospermopsis genus caused a similar blue green algae outbreak in the lake and channel that lasted several months in early 2024.
This freshwater algal bloom has no connection to the ongoing marine Karenia mikimotoi microalgae bloom currently affecting beaches on the Fleurieu Peninsula, Yorke Peninsula and Kangaroo Island.
People living in the area or visiting parts of the lake and near Goolwa Channel can still enjoy boating and fishing, but are strongly advised to take extra care not to ingest the water.
Unlike other blue green algae, the species detected at Lake Alexandrina generally does not form scums and is not easily visible to the naked eye.
If you have been in the water at Lake Alexandrina and you start feeling unwell, seek help from your GP and say you may have been exposed to blue green algae.
Pets are particularly vulnerable and should be kept out of the water. The algae stick to pet fur and hair and can accumulate, giving higher exposure.
Fish caught in the lake should be cleaned and gutted thoroughly before consumption by humans.
Updates can change. For further information, visit the SA Health website.
