116 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Cyanophyta 

 Class Cyanophyceae 

 Order Hormogonales 

 Family Nostocaceae 

 GENUS APHANIZOMENON Morren, 1838 (fig. 52) 



MORPHOLOGY 



Cells are cylindrical or barrel shaped and rarely exceed 5 /*m in 

 diameter. They are united into straight or slightly curved trichomes, 

 which are laterally agglutinated by indistinct sheaths. Trichomes are 

 free floating. Intercalary heterocysts are cylindrical. Akinetes are 

 cylindrical. 



REPRODUCTION 



Reproduction is by heterocysts and akinetes. 



OCCURRENCE 



The single species, Aphanizomenon flos-aquae, is so consistently 

 related to hard water that it may be used as an index organism for high 

 pH and high contents of nitrogen, phosphorus, and carbonate. It is a 

 notorious component of algal blooms and occurs commonly with Ana- 

 baena and Anacystis. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 36.0 



pH 4.6 - 9.6 



Dissolved oxygen milligrams per liter 2.0 - 18.7 



Specific conductance micromho 11 -42,000 



Total alkalinity milligrams per liter 3 - 311 



Total hardness do 6 - 1,700 



Total nitrogen do .05- 24.0 



Total phosphorus do .0- 3.1 



SPECIES INFORMATION 



Refer to Smith (1920) and Prescott (1962). 



