BLue-green algae, or cyanobacteria, come in many forms and have generally gotten a bad press, mainly because five of the 2,000 identified species can produce some of the deadliest toxins known to science.
At the same time, they are one of the oldest organisms in the world, dating back 2.1 billion years, and we owe them thanks.
Cyanobacteria were the first organisms to use photosynthesis, which turns carbon dioxide into oxygen. They are responsible for creating the oxygen-rich atmosphere that enabled life on Earth to thrive and humans to evolve.
In their untold trillions, in almost every environment where there is water, even on moist rocks in deserts, they continue this valuable service, keeping the atmosphere safe for mammals to breathe.
But in nutrient-rich water, created by farm waste or sewage released into rivers and lakes, blue-green algae multiply rapidly, especially in warm sunshine. They are dangerous in still waters where they form dense rafts of scum that deoxygenate the waters and kill fish.
In some circumstances, they also create toxins that can poison animals and people who drink them. Only laboratory tests can determine whether such algal blooms are toxic, but anyone who sees one is advised to avoid it and she reports presence.
