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UPDATE: Orlando lifts alert for Lake Ivanhoe

April 23, 2021

LIFTED: Lake Alert for Lake Ivanhoe

Based on the latest results obtained by Florida Department of Environmental Protection (FDEP) from sampling Lake Ivanhoe on April 19, 2021, the Lake Alert for Lake Ivanhoe has been lifted. At this time, there are no toxins present in Lake Ivanhoe, but blooms may still occur. There are always risks that could be associated with swimming, recreating, or irrigating in and from water with algal blooms, please use your own caution. If you see a visible bloom present, please report it to the FDEP Algal Bloom Dashboard, which can be found here:

UPDATED Information – Lake Ivanhoe is being closely monitored for presence of microcystins (toxins) by City of Orlando and Florida Department of Environmental Protection (FDEP) staff. The City will continue to test Lake Ivanhoe and the City's tests will provide an update on the presence of microcystins, but the official toxin determination is obtained from FDEP’s laboratory data. At this time, the Lake Alert remains in effect until further notice.

Please continue to call the Lake Alert number, (407) 246-2220, for the most up-to-date information regarding your lake. During weekdays, the City's Lake Alert website, will also have the latest information.

Original Lake Alert:

On January 21, 2021 the city took water samples in Lake Ivanhoe to determine the presence of microcystins (toxins) resulting from an algae bloom in the lake. It was determined that potentially unsafe concentrations of toxins are present in Lake Ivanhoe. As a precaution, we are advising everyone to refrain from swimming, recreating and irrigating in/from Lake Ivanhoe 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. Due to this, the city will work closely with Florida Department of Environmental Protection (FDEP) to closely monitor Lake Ivanhoe. The city staff will continue to routinely test the lake, but the city's tests will only provide an update on the presence of microcystins. The official toxin determination is obtained from FDEP's laboratory data, and until the levels are deemed safe by state standards, the Lake Alert will remain in effect.

Please encourage your neighbors to register for the Lake Alert at so they too will get important information about Lake Ivanhoe directly.

In the meantime, as we stated above, the city would a