Anabaena flos-aquae (light micrograph)
Anabaena is a filamentous (forming chainlike series of cells) species of alga belonging to a group known as cyanobacteria, or blue-green algae. Anabaena occurs in fresh water bodies throughout Florida. It can form blue-green surface clumps or be distributed throughout the water column. In Florida, large concentrations of Anabaena, called blooms, usually occur in summer and fall months and are common in the St. Johns River. Anabaena produces several types of toxins that can affect the nervous system and the liver.