112 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Cyanophyta 

 Class Cyanophyceae 

 Order Hormogonales 

 Family Nostocaceae 

 GENUS ANABAENA Bory, 1822 (fig. 50) 



MORPHOLOGY 



Cells are spherical to barrel shaped, are homogeneous or granulose, 

 and sometimes contain pseudovacuoles. They are united into free- 

 floating, beadlike trichomes that are solitary or aggregated. Trichomes 

 are cylindrical or slightly attentuated at the apices. They may be 

 straight, circinate, or spirally or irregularly twisted. Intercalary 

 heterocysts are spherical. Akinetes are variously shaped. 



REPRODUCTION 



Reproduction is by heterocysts and akinetes. 



OCCURRENCE 



The genus is found commonly in the euplankton and tychoplankton of 

 hard water or eutrophic water during periods of high temperature. It is 

 a frequent component of algal blooms and is indicative of hard water 

 having a high nutrient content when occurring with Aphanizomenon or 

 Anacystis. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 37.0 



pH 4.4 - 9.6 



Dissolved oxygen milligrams per liter .4 - 19.0 



Specific conductance micromho 12 -30,000 



Total alkalinity milligrams per liter - 371 



Total hardness do 5 - 1,600 



Total nitrogen., do .00- 18.0 



Total phospnorus do .0 - 3.5 



SPECIES INFORMATION 



Refer to Geitler (1932) and Prescott (1962). 



