Natural Highlights: Cyanobacteria

     Microcystis sp.

There has been a recent spate of tragedies involving pets and toxins produced by Cyanobacteria.  Most have occurred in late summer when high temperatures help to create conditions which spur the growth of bacteria and algae in ponds and lakes, while also tempting people to let their dogs play in the water.   

The Cyanobacteria are commonly called "blue-green algae" but they are not algae at all; they lack a nuclear membrane and thus belong in the same kingdom as the bacteria.  The Cyanobacteria do photosynthesize using chlorophyll, which explains their typical coloration, and some species form long filamentous colonies which are easily confused with filamentous green algae.  From the perspective of public safety, the most important difference is that green algae are generally harmless while some species of Cyanobacteria can release deadly toxins which can kill wild and domestic animals, and people as well.  Most of these toxins affect the liver and/or the kidneys; some attack the nervous system.

Cyanobacteria are ubiquitous in aquatic habitats, along with many other microscopic organisms, but when conditions are right, population growth can explode in a "bloom" accompanied by cell death and decomposition.  Most known Cyanobacteria species are not harmful, but the ones that are can be deadly. Toxins are most often released during decomposition, and they can concentrate in the drying masses of filaments than often accumulate along a shoreline, besides poisoning the water.  Microcystis, pictured above, is a genus of Cyanobacteria which is often the culprit in toxic blooms.

Ideal conditions for toxic blooms in freshwater can be found in still, warm waters that receive abundant sunlight and nutrient inputs (fertilizer, livestock, pet waste).  Many urban ponds and lakes, often in public areas, meet these qualifications and should be approached with caution. Saltwater can also be affected. The coasts of Mississippi and Florida have been plagued with blooms this year, and nutrient pollution from the Mississippi River and coastal communities is partly to blame, along with high temperatures.

These are the last dog days of summer.  Until conditions change, it's probably better to provide the pups with a baby pool in the backyard.  

Learn more about the Cyanobacteria at these links:



Posted by Cathy Justis at 9:41 AM