Small amounts of this cyanobacteria can be found in bodies of water worldwide,[1] but it is notable for growing prolifically in Upper Klamath Lake, Oregon.

Aphanizomenon flos-aquae was historically treated as a single homogeneous species, but genetic technology reveals significant diversity within the group, with at least 18 separate genomes[6] identified and potentially over 100 awaiting classification.

However, research employing genetic sequencing and species-specific analysis has revealed that these toxins were not capable of being produced by Klamath AFA itself[14][15][16] but were instead the result of cross-contamination from co-occurring toxin-producing cyanobacteria inhabiting the same environment.

[17][18] While this subspecies has been detected in other water bodies,[19] these populations are either too sparse or are mixed with other aquatic species, making harvesting impractical.

Klamath Lake's high levels of dissolved minerals, large surface area, shallow depths, and other nutritional and environmental factors create suitable conditions for the proliferation of Aphanizomenon flos-aquae MDT14a.