CHAPTER 9 



The food chain in the sea 



Food is indeed so important that it must have a chapter to itself although 

 it has so often necessarily been mentioned in the preceding chapters. The 

 distribution of plankton is dependent on its food supply, and the structure of 

 the various species is closely related to the type of food they cat, the method 

 of feeding and the way they fmd their food. The reader will already have 

 grasped the main principles of the food chain in the sea, but these need to be 

 reiterated and elaborated: they are shown in Fig. 31, where the complicated 

 story is reduced to very simple terms. 



SU/VS ENERGY 



Rtgeneration 

 of nutrients. 



Excretions and 

 wastt products . 



OXYGEN AND CARBON DIOXIDE 

 from thQ atmosphtre 



NLfTRIENTS 



from 



sewage a land droinagz 



Plant growth 

 (PHYTOPLANKTON) 



Regeneration 

 of nutrients. 



Death and decay 

 by bacteria. 



feeders. 

 CZOOPLANKTON) 



Protozoa&detritus y\ Carnivores. 



Bottom 

 fauna. 



Herbivores. 

 CZOOPLANKTON) 



CZOOPLANKTON) 



\ 



Excretions and 

 waste products 

 (including oxygen 

 from plants) 



Demersal fish. 



f^AN 



Fig. 31. Diagram of the most important elements in the food cycle in the sea. 



