Chapter 9 



Organic Sources of Nitrogen for 

 Marine Centric Diatoms* 



Robert R. L. Guillard 

 INTRODUCTION 



A here is little information on the capacity of marine diatoms 

 to use organic compounds as nitrogen sources. Experiments with 

 natural populations of diatoms and bacteria led Harvey (11) to 

 conclude that amino acids were not utilized significantly unless 

 first deaminated by bacteria, but that uric acid and urea were. 

 Trimethylamine, an excretory product of fishes, was not used at 

 all. 



Various marine flagellates and green algae have been exam- 

 ined for ability to use organic nitrogen. Some of these species 

 inhabit environments (e.g., rock pools) where the amount of 

 organic material is at times high. Such studies were made by 

 Schreiber (23), Braarud and F0yn (1), Droop (4, 5), Gibor (8) 

 and McLaughlin (17). No organic sources were suitable for all 

 species, but the data suggest that uric acid and urea are the ones 

 most generally utilized. Two species require amino nitrogen: the 

 photosynthetic cryptomonad Hemiselmis virescens grows best on 

 glycine (4), while the colorless phagotrophic dinoflagellate 

 Oxijnhis marina could not use glycine but grew on xaline, proline, 

 or alanine. 



The growth of the attached green alga Prasiola stipitata 

 (which often occurs in association with the excreta of gulls), was 

 stimulated by 0.1 per cent glutamate or asparagine, but had no 

 absolute requirement for an organic source of nitrogen ( 15 ) . 



A few fresh water green algae have been studied intensively 



* Contribution No. 1195 from the Woods Hole Oceanographic Institution under 

 contracts AT (30-1) -2646 and 1918 with the U. S. Atomic Energy Commission 

 and with the partial support of NSF Grant 10693. 



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