Nutritional Characteristics of Some Chrysomonads 115 



nads, we have established bacteria-free cultures, by treatment 

 with antibiotics and micropipette washings of the following 

 chrysomonads kindly given to us by Dr. Mary Parke of the 

 Plymouth Laboratory, who had isolated them in unialgal culture: 

 CoccoUthus huxleyi 92a, Pavlava ^yrans 93, OchrospJiaera nea- 

 politana 162, Sijracosphaera sp. 181, and Hymenomonas sp. 156. 

 All grow autotrophically in chemically defined media: Pavlova, 

 SyracospJiacra and Hymenomonas prefer DV (10); and 

 Ochrosphaera and CoccoUthus grow best in ASP12NTA, a medium 

 originally designed for high-salinity algae by Provasoli ( 7 ) . 



NUTRITIONAL REQUIREMENTS 



Salinity Tolerance 



Different salinities were achieved by keeping constant the 

 enrichment (N, P, trace metals, vitamins, and pH buffer) and 

 varying (in the same proportion as in the above media) the 

 concentrations of Na, Ca, K, and Mg. CoccoUthus huxleyi and 

 Ochrosphaera are stenohalines of oceanic type; on the contrary 

 Syracosphaera, Hymenomonas and especially Pavlova are wide- 

 range euryhalines (Table I). While Pavlova and Syracosphaera 

 do not show a well defined salinity optimum, Hymenomonas 

 definitely prefers the 12 to 32 per mil range. The in vitro data 

 for C. huxleiji con-espond rather closely with the field obsen^a- 

 tions of Braarud (4, 5): C. huxleyi was found in the sea and 

 polluted waters of the Oslofjord at salinities of 18%c or above. 

 Pavlova, the most euryhaline, lives in the brackish dilute Baltic 

 Sea. 



Vitamin Requirements 



The 5 species need vitamins. With the accumulation of data 

 a chrysomonad pattern for vitamins is emerging. The thiamine 

 requirement is predominant over B12; biotin, an uncommon re- 

 quirement for other algal groups, is needed by some freshwater 

 chrysomonads. As for the marine species, SticliocJirysis immohilis 

 does not need vitamins, Hymenomonas carierae requires only B12; 

 Pleurochrysis schei'ffelii, CoccoUthus huxleyi, Ochrosphaera 

 neapolitana, Syracosphaera 181, and Hymenomonas 156 require 

 only thiamine; Hymenomonas elongata, Isochrysis galhana. 



