The presence of a mass of cyanobacteria (blue-green algae) is commonly referred to as a bloom. It is well known that cyanobacteria dominate aquatic plant (phytoplankton) communities when these conditions occur:

  • There is a stable water column over a sufficient period of time
  • Warm water temperatures (15-30°C) are present
  • High nutrient levels exist, especially when there is a low nitrogen to phosphorous ratio
  • There is high light intensity

Masters of Survival

Cyanobacteria possess some unique adaptation characteristics (physiological, morphological, and ecological) that result in their blooming when the conditions are favorable. Different species have developed special bloom strategies. Epilimnetic and metalimnetic bloom-forming species are largely successful by regulating buoyancy, moving vertically through the water column, providing access to maximum light, heat, and inorganic carbon. In sufficient concentration they then dominate the euphotic zone of eutrophic lakes. Surface blooms may be the result of mass recruitment of buoyant cells and/or colonies attracted to the uppermost layer of the water column. It is widely accepted that while surface blooms are a natural occurrence, anthropogenic eutrophication is resulting in increased occurrence and severity, both in magnitude and duration, of these blooms.

Unpredictable Surprises

The hidden surprise that often comes with some cyanobacterial blooms is the release of toxins into the water supply. It is generally understood that cyanobacteria bloom formations and toxin concentrations are not predictable. Severe blooms may or may not produce high toxin levels. Similarly, lesser blooms may provide high or low levels of toxins. Further studies are required to ascertain the relationship of bloom formation, the environment, and their related toxins. Read more about toxins.

An Ounce of Prevention
The best way to avoid the problems of cyanobacterial blooms is to prevent blooms from forming. In a perfect world, this is done by influencing the growth factors that can reasonably be controlled–such as reducing the input of phosphates into the water source. Practically speaking, that is not always possible. So the most environmentally friendly option is to treat the bloom without introducing elements that impose yet another environmental risk. Using PAK®27 as an algaestat is an environmentally safe and cost-effective method for controlling blooms.

A Lay Person's Guide to Aquatics

Anthropogenic eutrophication – The result of humans imposing an (artificial) supply of nutrients into the water, such as the nitrogen- and phosphorous-rich environment created by fertilizer runoff.

Epilimnetic — Concerning the upper water layer in a temperature-stratified body of water.

Euphotic — Concerning the upper, illuminated part of a body of water.

Eutrophic — Nutrient-rich, and hence usually biologically active.

Metalimnetic — Concerning the intermediate, subsurface layer of a temperature-stratified body of water, just above the thermocline.

Thermocline — The imaginary plane in a body of water that separates the oxygen-rich, warmer water from the colder, oxygen-deprived lower layers