88 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chrysophyta 

 Class Bacillariophyceae 

 Order Pennales 

 Family Nitzschiaceae 

 GENUS NITZSCHIA Hassall, 1845 (fig. 38) 



MORPHOLOGY 



Cells are solitary and free floating or densely clustered in unbranched 

 gelatinous tubes. They are generally elongate and extremely varied in 

 outline, having somewhat attenuated poles. Valves are longitudinally 

 asymmetrical. Keeled margin of one valve faces unkeeled margin of 

 other valve. The raphe lies within the keel and has small central and 

 polar nodules. A rapheal fissure has a uniseriate row of conspicuous cir- 

 cular pores (carinal dots) opening toward the interior of the cell. Striae 

 or punctae are transverse. Two chromatophores on same girdle face 

 are axial. 



REPRODUCTION 



Protoplasts of 2 approximate cells each form 2 gametes. Union of 

 gametes forms 2 auxospores. 



OCCURRENCE 



The genus has a widespread distribution and is found in all types of 

 waters. Some species are indicative of particular environmental condi- 

 tions (Patrick, 1948, 1973). According to information included in this 

 report, Nitzschia is the most commonly occurring genus in the 

 phytoplankton of the United States. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 ■ 



pH 3.4 - 



Dissolved oxygen milligrams per liter .2 ■ 



Specific conductance micromho 10 



Total alkalinity milligrams per liter 



Total hardness do 3 



Total nitrogen do .00- 



Total phosphorus do .0 - 



SPECIES INFORMATION 



Refer to Boyer (1927a). 



