BLUE-GREEN ALGAE 



Blue-green algae are a very diverse group, being classified primarily 

 by cell pigmentations that produce an overall bluish-green coloration 

 to the plants. These plants, like green algae, grow as individual cells 

 (unicellular) or in filamentous colonies, depending on genera. Many 

 of the filamentous colonial types produce gelatinous coatings that 

 sheath the cell walls. A number of species produce colonies, such as 

 the jelly-balls of Nostoc and the tough, compact mats of 

 Phormidium . Blue-green algae are usually found growing in 

 association with filamentous green algae. A few typical blue-green algae 

 found on irrigation systems are illustrated; a habitat sketch is shown 

 on the left and a microscopic view of the plant cells that make up the 

 filaments on the right. 



The upper left portion of the drawing shows the typical "jelly-ball" 

 of Nostoc, which will be highly variable in size and is observed either 

 free-floating or resting on the bottom of a canal or pond. These algae 

 can cause problems in plugging siphon tubes and pumps. 



The second illustration shows free-floating Aphanizomenon 

 colonies. This species gives an impression of lawn grass clippings 

 floating in water. This plant could, in certain situations, become a 

 menace to mechanical water conveyance equipment, as well as create 

 a taste-odor problem to potable water. 



One of the blue-greens that has caused some hydraulic problems 

 to lined conveyance channels is Phormidium . Colonies of this species 

 can become fixed to a canal lining and produce thick, tough, gelatinous 

 masses, thus not only reducing the capacity of the channel but causing 

 fouling of pumps, hydroelectric generators, and siphon tubes as the 

 mats break apart. 



The lower illustration is Anabaena, a species that can, upon 

 decomposition, produce taste-odor problems as well as soluble 

 substances that can be toxic if ingested in quantity by mammals. This 

 is a very common species frequently found floating on the water 

 surface in dense gelatinous masses that have a rather moldy 

 appearance. 



44 



