Orlando issues alert for Lake Holden
On February 22, 2021 the City of Orlando was made aware of the presence of microcystins (toxins) in Lake Holden resulting from an algae bloom in the lake (samples taken by the Florida Department of Environmental Protection). It was determined that potentially unsafe concentrations of toxins are present in Lake Holden. Because of the potential for harm to humans and pets, we are advising everyone refrain from swimming, recreating, and irrigating in/ from Lake Holden until further notice.
For reference, cyanobacteria/blue-green algae are always present in the water, however, not all bacteria have the ability to produce toxins. Toxicity is hard to predict because a single species of algae can have toxic and non-toxic strains. This instance is believed to have occurred due to the water in the lake "flipping." During the colder months, the warm surface water begins to cool. As water cools, it will become more dense, causing it to sink. This dense water forces the water of the bottom layer to rise, turning the layers over. The bottom layer tends to be very nutrient rich, then is exposed to sunlight at the surface level and causes an algae bloom to occur.
Nothing can be done to treat algae blooms without causing massive fish kills. The city will continue to closely monitor and routinely test Lake Holden. The Lake Alert will remain in effect until no toxins are detected.
Please encourage your neighbors to register for the Lake Alert at orlando.gov/lakealert so they too will get important information about Lake Holden directly.
In the meantime, as stated above, the City would advise refraining from swimming, recreating and irrigating in/from the lake until further notice.
If you should have additional questions, please email Lisa Lotti at