42 ALGAE IN PHYTOPLANKTON OF THE UNITED STATES 



Division Chlorophyta 

 Class Chlorophyceae 

 Order Chlorococcales 

 Family Scenedesmaceae 

 GENUS SCENEDESMUS Meyen, 1829 (fig. 15) 



MORPHOLOGY 



Cells are ellipsoidal, oblong, fusiform, acicular, or ovoid. The single 

 chromatophore is parietal. Cell walls are smooth, corrugated, 

 granulate, or spicate with or without marginal or lateral teeth or 

 spines. Coenobia are flat and consist of 2, 4 (most commonly), or 8 cells 

 but sometimes as many as 16 or 32 cells. 



REPRODUCTION 



Transverse and longitudinal divisions into 2, 4, 8, 16, or 32 

 autospores are undertaken by a parent cell. The parent-cell wall splits 

 longitudinally, releasing the daughter colony. 



OCCURRENCE 



The genus is widely distributed in the euplankton, tychoplankton, 

 and periphyton. It is found in all types of waters. The commonly occurr- 

 ing species, Scenedesmus quadricauda, is one of the most nearly ubi- 

 quitous algal species. Great numbers, so as to color the water green, 

 may occur in small pools. 



ENVIRONMENTAL CONDITIONS 



Standard 

 Range Mean deviation 



Temperature degrees Celsius 0.0 - 37.0 18.1 8.4 



pH 3.4 - 10.0 7.6 .7 



Dissolved oxygen milligrams per liter .1 - 22.0 8.7 2.5 



Specific conductance micromho__ 10 -48,000 863 1,800 



Total alkalinity milligrams per liter - 480 119 80 



Total hardness do 3 - 2,000 221 254 



Total nitrogen do .00- 26.0 1.6 2.0 



Total phosphorus.. do .0 - 4.0 .2 .3 



SPECIES INFORMATION 



Refer to Chodat (1926), Smith (1916), and Prescott (1962). 



