Organic Sources of Nitrogen for Marine Centric Diatoms 95 



TABLE 1 

 Medium 'f' 

 Sea Water 1 liter 

 NaNOs 150 mg (1.765 mM) 

 NaH^POrH.O 10 mg (72.5 /iM) 

 Na.SiO.-9H.O 30 mg (10>/iM) 

 Ferric sequestrene (1) 10 mg (1.3 mg Fe) 

 CuS04-5H,0 0.0196 mg (0.005 mg Cu) 

 ZnS04-7H20 0.044 mg (0.01 mg Zn) 

 CoCL-6H.O 0.02 mg (0.005 mg Co) 

 MnCl2-4H,0 0.360 mg (0.1 mg Mn) 

 Na.Mo04-2H20 0.0126 mg (0.005 mg Mo) 

 Thiamine -HCl 0.2 mg 

 Biotin 1.0 /ig 

 B^^ 1.0 /tg 



^ Ferric sequestrene (Geigy Industrial Chemicals, Saw Mill River Parkway, 

 Ardsley, New York) is the sodium iron salt of ethylene diamine tetra acetic 

 acid, 13 per cent iron. 



At 100 uM of inorganic nitrogen, the yield of most of tlie 

 algae was shown to be limited by the quantity of nitrogen nnder 

 the experimental conditions. 



When growth in flasks containing nitrate or ammonia was 

 approximately maximum, yields were measured in all flasks. 

 Tlie yields without added nitrogen (item 1 above, amounting 

 at most to 5 per cent of the maximum yields) were subtracted 

 from the yields in all other treatments ( items 2, 3, 4 ) to detemiine 

 the growth due solely to the added nitrogen sources. The fraction 

 (growth on organic source/growth on inorganic source), ex- 

 pressed as per cent, was taken as a measure of capacity to use 

 the nitrogen source in question. Treatment (4) was included 

 to detect possible inhibition by the organic compounds. 



Those flasks containing organic sources in which the algae 

 had grown comparatively little at tlie time yields were measured 

 were observed for a longer time to see if growth occurred, indi- 

 cating adaptation. It was also noted if the final yields approached 

 the yields with nitrate in a reasonable time. 



Culture Conditions and Methods 



Stock cultures were grown in 50 ml of autoclaved medium 



