Cultivation of Marine Organisms as a Means of 



Understanding Environmental Influences on 



Populations 



TRYGVE BRAARUD 



Institute for Marine Biology, University of Oslo, Oslo-Blindern, Norway 



AT a symposium on "Perspectives in Marine Biology" a few 

 years ago the distinguished oceanographer Dr. Alfred C. Redfield 

 gave a paper with the rather provocative title: "On the inade- 

 quacy of experiments in marine biology" (Redfield, 1958). Al- 

 though admitting the great value of contributions from physiolo- 

 gists, Redfield concluded that "the greater need at the moment is 

 more knowledge of the phenomena to be explained." One can 

 follow Redfield a long way in his argument for intensifying the 

 study of conditions in the sea in order to obtain a more precise 

 description of the qualitative and quantitative distribution of 

 populations as related to environmental factors. However, marine 

 biologists working on field ecological studies may not in general 

 wholeheartedly agree with his conclusion. It may not be wrong 

 to say that there is a general feeling among marine ecologists that 

 precisely the combination of field work and laboratory experi- 

 ments is essential to progress in the biological field of oceanography. 

 Another question is whether this feeling is sustained by the results, 

 which have so far been achieved through experiments. The general 

 title of this paper is so wide that it will be necessary to illustrate 

 the experimental approach with the use of cultures by examples 

 and these have been chosen from my own field of marine phyto- 

 plankton. I would like to make it clear that I have chosen to ab- 

 stain from dealing with the more general studies of, say, plant 

 physiology, which undoubtedly are of the greatest value for the 



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