62 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Fragilariaceae 

 GENUS ASTERIONELLA Hassall, 1850 (fig. 25) 



MORPHOLOGY 



Cells are joined to one another at their ends to form flat stellate col- 

 onies. Cell length may reach 130 /*m; cell diameter is about 1-2 ^m. 

 Valves are linear with inflated ends and are symmetrical in valve and 

 girdle views. They are finely transversely striated. Intercalary bands, 

 septa, and costae are lacking. The pseudoraphe is indistinct. There are 

 2 (generally) to several lobed chromatophores. 



REPRODUCTION 



Reproduction is probably by the formation of an auxospore within a 

 single cell. 



OCCURRENCE 



Asterionella is a commonly occurring alga in the euplankton. It is in- 

 dicative of mesotrophic to eutrophic conditions. They may occur in such 

 abundance as to impart a fishy taste to the water (Whipple and others, 

 1948). 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius__ 0.0- 31.0 10.6 7 5 



pH 4.7 - 9.4 7.6 .6 



Dissolved oxygen milligrams per liter 2.0 - 16.6 10.3 2.2 



Specific conductance micromho__ 19 -8,000 342 389 



Total alkalinity milligrams per liter - 371 92 63 



Total hardness do 2 -1,400 127 104 



Total nitrogen do .01- 14.0 1.13 1.14 



Total phosphorus do .0-2.3 .1 .1 



SPECIES INFORMATION 



Refer to Meister (1912), Boyer (1927a), and Patrick and Reimer 

 (1966). 



