Chapter 23 



Heterotrophy in Marine Diatoms t 



Joyce C. Lewin 

 INTRODUCTION 



D 



iatoms can generally grow autotiophically by photosynthesis, 

 manufacturing from CO2 and HjO in the presence of light all or 

 almost all of the organic matter that they need for their life 

 activities. It is of some ecological interest to know whether or not 

 marine diatoms can also grow heterotrophically, i.e., in darkness 

 in the presence of a suitable carbon source. If such heterotrophic 

 growth can take place, then some diatom species might actually 

 be able to multiply in ocean depths where light does not pene- 

 trate, beneath the surface of mud, etc. Approximately 39 species 

 (60 isolates) of marine diatoms now maintained in bacteria-free 

 cultures in the laboratory have been tested for their ability to 

 multiply under heterotrophic conditions; the results are presented 

 below. 



Isolates Studied 



Forty-four isolates of marine littoral diatoms, comprising 

 species of pennate diatoms such as Nitzschia, Navicula, and Am- 

 phora spp. and including one centric species, were tested for 

 their ability to grow heterotrophically (4). In addition, some 

 interesting and ecologically important strains isolated by Dr. R. 

 Guillard (Woods Hole Oceanographic Institution), comprising 

 marine littoral and planktonic centric species, subsequently also 

 have been tested for heterotrophic growth. 



* Contribution from Scripps Institution of Oceanography. New Series. 



t These studies were aided by a contract between the Office of Naval Research, 

 Department of the Navy, and the Scripps Institution of Oceanography, Nonr- 

 3221(00), and by a grant from the National Science Foundation, G-15068. 



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