The Halifax Regional Municipality is warning residents to avoid swimming in the lake or coming into contact with the lake water until further notice.
In a release on Tuesday afternoon, HRM says that if you come into contact with the water, to wash it off with tap water as soon as possible.
They also include pets in the advisory, saying not to allow your pets to swim or wade in the lake, especially where blue-green algae is visible. You should also avoid consuming any fish that come from the lake.
The off-leash dog area of Shubie Park at Lake MicMac will also be closed to swimming until further notice.
People who ingest or come into contact with blue-green algae may experience negative effects, including skin irritation, rash, sore throat, sore red eyes, swollen lips, fever, nausea and vomiting and/or diarrhea.
HRM staff advise anyone who has these symptoms to seek medical assistance, and warns that children and immune-compromised people are at a higher risk.
Blue-green algae (cyanobacteria) is naturally occurring in freshwater environments and may become visible when weather conditions are calm.
When the algae rapidly multiplies in hot weather, it creates a bloom. When blooms decay, toxins from the algae may be released into the water, posing a risk to people and pets.
Although HRM say they don't know whether this bloom contains toxins, they will be testing it.
If the algae bloom is toxin producing, further testing will be carried out and the risk advisory will remain in effect until blooms have disappeared and test results indicate water is within safe limits.
For more information, visit the Halifax website's page on algae blooms.