Cyanobacteria are single-celled germs that produce harmful toxins. You can think of them as tiny sacs filled with different kinds of poisons. Depending on the kind of cyanobacteria and the way you are exposed, the toxin may affect your nervous system, eyes, skin, nose and throat, lungs, or gastrointestinal tract. The toxins are not released until the cell dies. Thus, there may be a lot of cyanobacteria in the water, but testing for dissolved toxin is negative. Once all the cells die, toxin levels still may remain high for a week or two.

You may be exposed if you touch or drink the water or breathe in the spray from a propellor or someone splashing. Cyanobacteria are not contagious, like coronaviruses, but you may become ill from petting your wet dog’s fur.

The amount of toxin exposure is important: you will not get sick from one cyanobacteria. A small child or or pet becomes ill with less toxin than would an adult. If there are enough germs that you can see them on the surface as a blue-green or reddish scum, there is probably enough toxin to make you ill.

A cyanobacterial bloom (cyanoHAB) occurs when a large number of germs rise to the surface all at once forming a visible scum. The wind can blow them elsewhere as soon as they come to the surface, so you can’t tell from the location of the scum where all the cyanobacteria are.

If a visible scum is reported, the TriTown Health Department will confirm it and report it to the Department of Public Health. An advisory will be posted not to drink or enter the water or come into contact with it. The water will be tested weekly for dissolved toxin and cell count. Once the visible scum has dissipated and the tests are negative for two consecutive weeks, the advisory will be lifted.