118 Marine Microbiology 



organisms was lower than nitrate, either as N or weight of com- 

 pounds. 



The five species differed in tolerance toward (NH4)l>S04: 

 C. huxleyi did not utilize it in the range 0.01-1 mg %, the latter 

 concentration being toxic. The other chrysomonads utilize am- 

 monia (the best concentration is 10 mg %) and only Pavlova and 

 Hymenomonas can withstand 20 mg %. It is interesting that these 

 species are resistant to ammonia in the alkaline range since 

 Prymnesiwn pawiim is so sensitive to it that ammonia salts are 

 employed to prevent poisonous outbreaks of Prymnesitim in the 

 dilute brackish fish ponds in Israel. This toxicity declines sharply 

 with salinity (20 mg % (NH4)2S04 is inhibitory at 16^^^^ and toxic 

 at S%c) and ammonia is a good N source for Pnjmnesium in tlie 

 neutral or acid range (9). 



Carbon Sources 



The following carbon sources were tried at 10-50 mg % 

 (the stimulatory ones were tried at higher concentrations): 

 acetic, fumaric, aspartic, succinic, lactic, glutamic, pyruvic 

 (aseptic addition), and malic acids; alanine, asparagine, glycine, 



TABLE 2 



Growth Response to Carbon Sources in Light (Optical Density; 

 1 Month Growth) 



