PLANKTON 29 



Fogg's monograph 40 offered an invaluable compilation of facts on the 

 metabolism of algae. In the same year, the Carnegie Institution issued 

 "Algal Culture: from laboratory to pilot plant" 41 ; this volume, collected 

 and edited by Burlew, made available extensive data on algal metabolism 

 and culture. Additional data on the metabolic aspect of algal growth was 

 provided in the "Growth of Protozoa," 190 issued in 1953 by the New 

 York Academy of Sciences. 



2. Metabolism, Culture, and Nutritional Values 



Even more so than with zooplankton, the recent intensive interest 

 in phytoplankton has been sparked by the growing disparity between 

 world population and food supply. 191 - 192 The attractiveness of phytoplank- 

 ton as a food is enhanced by several inherent qualities: Practically all of 

 it is digestible, in contrast with higher plants, which contain a large pro- 

 portion of cellulose. The protein content is higher than in field plants, 

 it is of low molecular weight, and it contains most of the required amino 

 acids. Under controlled conditions, an excellent lipid yield can be achieved. 

 Vitamins and minerals are present in abundance. And, best of all, algae 

 can be cultivated and almost always be maintained at a maximal growing 

 rate, whereas land crops utilize sunlight most efficiently only just before 

 harvest. Interesting comparative figures are offered in Table III. 



Microscopic algae have a basically simple cellular structure. 193-196 

 Like other pigmented plants, the algal cell usually comprises a nucleus, 

 one or more chloroplasts, and a cytoplasm containing various formed 

 structures. The pigments are generally concentrated in the chloroplasts, the 

 "solar engines" which are now considered the main sites of photosynthetic 

 activity. 197 Here the pigment enables algal cells to convert inorganic to 

 organic substances by utilizing radiant energy. 198 



The key pigments involved in algal photosynthesis (as condensed 

 from Fogg 40 ) are shown at the top of page 31. 



The chlorophylls and carotenoids are both fat soluble. The former 

 embody a cyclic tetrapyrrolic nucleus with magnesium ; the latter generally 

 contain about 40 carbon atoms. The carotenes are hydrocarbons, while the 

 xanthophylls are oxygen derivatives of the carotenes. The phycobilins 

 differ from the other pigments in being soluble in water but not in fat 

 solvents. They resemble the chlorophylls in possessing a tetrapyrrolic 

 nucleus, but the latter is linear instead of cyclic, and is linked to a 

 globulin instead of to a metal. 



