Overview
What Is Blue-Green Algae?
Cyanobacteria, also called "blue-green algae" are relatively simple, primitive life forms closely related to bacteria. Typically much larger than bacteria, they photosynthesize like algae. Depending upon the species, cyanobacteria can occur as single cells, filaments of cells, or colonies. Cyanobacteria contain a characteristic pigment which gives the group their blue-green coloration. When cyanobacteria blooms begin to die and disintegrate, this pigment may color the water a distinctive bluish color. Cyanobacteria are found throughout the world in terrestrial, freshwater and marine habitats, but blooms typically occur in freshwater.
What is a blue-green algae bloom?
Nutrient-rich bodies of water such as some lakes or ponds may support rapid growth of cyanobacteria. With the right conditions, a "clear" body of water can become very turbid with green, blue-green or reddish-brown colored algae within just a few days. High concentrations of an alga species in a water body form "blooms." Many species can regulate their buoyancy and float to the surface to form a thin "oily" looking film or a blue-green scum several inches thick. The film may be mistaken for a paint spill. Cyanobacteria cannot maintain this abnormally high population for long and will rapidly die and disappear after one to two weeks. If conditions remain favorable, another bloom can quickly replace the previous one. In fact, successive blooms may overlap so that it may appear as if one continuous bloom occurs for up to several months.
Why is blue-green algae a problem?
Blue-green blooms can pose a human health concern. Although most blue-green blooms are not toxic, some blue-green algae produce nerve or liver toxins. Toxicity is hard to predict in part because a single species of algae can have toxic and non-toxic strains. Also a bloom that tests non-toxic one day can turn toxic the next day. People may become ill after swimming or water skiing in lakes with toxic blue-green algae. Rarely, humans may experience stomach pains, vomiting, diarrhea, and skin rashes. Nerve and liver damage have been observed following long-term exposure such as drinking water with toxic blooms. Pets and wildlife have died after exposure to toxic blue-green algae.
What can we do about blue-green algae?
The long-term solution for controlling blue-green algae involves finding ways to reduce nutrient inputs into the water body. There are also best management practices that lake residents can follow that may help reduce nutrients or algae problems. Well-designed, continuous, year-round diffused aeration at the bottom of the lake can minimize the natural recycling of phosphorus from the sediment.