BLUE-GREEN algae has been detected in Lake Glenmaggie and Lake Wellington, and authorities are warning people not to swim, fish or come into contact with the water.
The algae can be dangerous to humans and animals, often causing skin rashes or itchiness, sore eyes, ears and nose or, if swallowed, gastroenteritis, nausea or vomiting.
Boiling the affected water will not make it safe for use.
People who come into direct contact with contaminated water should wash immediately in fresh water.
If experiencing a health issue related to contact with water contaminated by blue-green algae, people should seek medical advice.
Department of Environment, Land, Water and Planning algae bloom Gippsland regional coordinator Chris Barry said people should avoid contact with affected water, particularly where floating scums, discoloured water or clumps of algae were evident.
“Inhalation of fine droplets can cause mild respiratory effects and symptoms similar to hay fever,” he said.
“Drinking algae-affected water or consuming fish containing toxins can lead to gastroenteritis.
“These toxins may also affect the liver or nervous system.
“The water can also affect animals, so do not allow pets to swim in it,” he said.
Mr Barry said while anglers were advised not to eat fish caught from Lake Wellington and Glenmaggie, seafood and fish bought from local shops, served in cafés and restaurants or supplied by commercial fisheries were not affected and were completely safe to eat.
Other parts of the Gippsland Lakes, including Lake Victoria, Lake King and Lakes Entrance, are safe for recreational water use.
Warning signs advising the public of the situation will be installed at Marlay Point and around Lake Glenmaggie.
Organisers of the Marlay Point Overnight Race are aware of the situation, and will be advising participants of necessary precautions.
The warm weather and low freshwater inflows have contributed to conditions suitable for algal growth.
Regular algal monitoring throughout the lakes will continue in coming weeks and the community will be informed about changes in those levels. Signs will be removed when the water is considered safe.
Blue-green algae can be invisible to the naked eye, or may form a scum.
Despite their name, blue-green algae are a type of bacteria, and are a naturally occurring component of freshwater environments.
According to Southern Rural Water, they are an essential part of a healthy body of water, as they produce oxygen and are themselves a source of food for certain aquatic animals.
In response to favourable conditions, they may undergo population explosions, called blooms, which can come and go quickly.
These conditions include still or slow-flowing water, hot days with abundant sunlight and sufficient levels of nutrients (especially nitrogen and phosphorus).
They affect water quality by causing undesirable tastes and odours, discolouration and unsightly scum.
During periods of drought, aquatic ecosystems can be severely degraded by algal blooms.