98 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Fragilariaceae 

 GENUS SYNEDRA Ehrenberg, 1830 (fig. 43) 



MORPHOLOGY 



Cells are narrow and generally very elongate. They are solitary or in 

 tufted, fan-shaped, or radiating colonies. They are free floating or 

 epiphytic, sessile, or contained in a gelatinous stalk. Cells are linear to 

 lanceolate, generally straight but sometimes slightly curved. Poles may 

 be attentuated and sometimes capitate. Transverse striae are lateral to 

 a conspicuous narrow pseudoraphe. The central area may be smooth or 

 striated. The two chromatophores are discoid. 



REPRODUCTION 



Either 1 or 2 auxospores may be formed within a cell. A "regenera- 

 tion" cell, which increases the size of the cell, has been observed by Ge- 

 meinhardt (1926). 



OCCURRENCE 



Synedra is widely distributed and is found in all types of waters. The 

 commonly occurring species generally occur in circumneutral water of 

 moderate to high conductivity, including brackish water. The genus is 

 generally indicative of mesotrophic to eutrophic conditions. It is found 

 in the euplankton, tychoplankton, and periphyton. 



ENVIRONMENTAL CONDITIONS 



Range 



Temperature degrees Celsius 0.0 - 37.0 



pH 3.7 - 10.0 



Dissolved oxygen milligrams per liter .2 - 20.7 



Specific conductance micromho 10 -49,800 



Total alkalinity milligrams per liter 3 - 491 



Total hardness do 2 - 1,900 



Total nitrogen do .00- 41.0 



Total phosphorus do .0 - 4.0 



SPECIES INFORMATION 



Refer to Boyer (1927a) and Patrick and Reimer (1966). 



