116 Marine Microbiology 



TABLE 1 

 Salinity Tolerance (Optical Density After 1 Month Growth) 



* Values for C. huxleyi isolated by R. Guillard from Sargasso Sea. 



Microglena arenicola, Monochrysis lutheri, Prymnesiwn parvum, 

 and Pavlova gyrans require B12 and thiamine. 



Trace Metals 



The requirement for trace metals seems low for all. At least 

 in the first transfer in media containing no trace metals, growth 

 is as good as with addition of various trace metal-chelate mix- 

 tures for Coccolithus and Ochrosphaera. For the other species 

 the addition of metal-chelated mixtures is slightly stimulatory; 

 however, a similar effect is obtained for Hymenomonas by simple 

 addition of a clielator (no added trace metals). These results 

 do not prove tliat Cu, Co, Zn, Mn, Fe are not needed, ratlier tliat 

 the need is low and is satisfied by the impurities brought in by 

 the "chemically" pure salts of the medium. In the absence of 

 metal chelators (as in "no trace metals") probably a part of tlie 

 heavy metals, perhaps significant, is in the form of a fine precip- 

 itate. If so, unexacting Coccolithus and Ochrosphaera may be 

 able to utilize precipitates; and the effect of the addition of a 



