28 GERLOFF, FITZGERALD, AND SKOOG 



the mineral nutrition of Coccochloris Peniocystis (Kiitz.) Drouet 

 and Daily also will be presented. This is the only species on 

 which detailed data have been obtained so far. 



Nutrient Solution for Blue-Green Algae Culture 



A survey of the literature indicated that nutrient solutions had 

 not been developed which were generally successful for the con- 

 tinuous culture of blue-green algae, a point also apparent from 

 other papers presented in this symposium. Several solutions were 

 tried which have been used extensively in investigations of green 

 algae and diatoms, and, of these, Chu No. lo, one of the seventeen 

 nutrient solutions published by S. P. Chu (1942), gave most 

 promising results. 



It was soon found that Chu No. 10 solution was improved 

 as a culture medium for blue-green algae by substituting an 

 organic source of iron, ferric citrate, for die ferric chloride speci- 

 fied by Chu. This improvement, due to increased iron availabil- 

 ity, also has been reported by Rodhe (1948). Furthermore, Rodhe 

 (I.e.) found by tests with o-phenanthroline that the addition of 

 an equal amount of citric acid with the ferric citrate stabilized 

 the concentration of reactive iron in the nutrient solution. This 

 modification was adopted. Therefore, the nutrient solution used 

 for the isolation work had the following composition in grams 

 per liter: Ca(N03)2, 0.04; K2HPO4, o.oi; MgS047H20, 0.025; 

 NasCOs, 0.02; NasSiOs, 0.025; ferric citrate, 0.003; and citric 

 acid, 0.003. The algae have been grown in 125 ml. Erlenmeyer 

 flasks containing 75 ml. of nutrient solution and have been kept 

 at approximately 25 °C. under continuous fluorescent light of ap- 

 proximately 40 foot candles intensity. 



With the above modification in the iron source, Chu No. 10 

 solution has been a satisfactory nutrient solution for the continu- 

 ous culture of twenty-four species of blue-green algae. It should 

 not be assumed, however, that it is the optimum culture medium 

 for any of the species. Nutritional studies with variations in the 

 amounts of essential elements in the solution may show that 

 modifications of Chu No. 10 will result in a faster rate and greater 



