L - • * Y 



RECENT WORK ON MARINE METABOLISM 



By JAS. JOHNSTONE, B.Sc. 



Fisheries Laboratory, University of Liverpool 



In a recent number of this journal l I reviewed a series of 

 memoirs on general marine physiology, the results of which 

 were: (i) that the density of both animal and vegetable life 

 is greater in the polar and temperate than in the equatorial 

 and sub-tropical seas ; (2) that these variations in the density 

 of life in the sea are to be associated with variations in the 

 abundance of certain " ultimate food-stuffs," probably ammonia 

 and nitric acid salts, soluble silicic acid, and phosphates ; and 

 (3) that the variations in the abundance of the first of these 

 inorganic food-salts depend upon the activity of certain forms 

 of marine bacteria, which possess the power of reducing nitric 

 to nitrous acid, nitrous acid to ammonia, and the latter to 

 elementary nitrogen. These bacteria are more active at the 

 temperature of tropical than that of temperate seas, and in 

 polar waters their activity is practically inhibited. Thus in the 

 warmer seas a certain proportion of the ultimate food-stuffs 

 available for the nutrition of the organisms of the vegetable 

 plankton is, so to speak, thrown out of circulation ; and to that 

 extent these waters are biologically impoverished. There is 

 actual experimental evidence for all these conclusions. 



It is assumed, in such a discussion, that there is a general 

 distinction between two categories of organisms in the sea : 

 (1) the " producers," algae, diatoms, other protophyta, and those 

 unicellular organisms which have a plant-like or holophytic 

 mode of nutrition. These organisms, by virtue of the power 

 of photo-synthesis which they possess, can elaborate starch 

 from carbon dioxide and water, and proteid from the carbo- 

 hydrate so formed and the nitrogenous food-substances absorbed 

 by them from their medium. Then we have (2) the " consumers," 

 the marine vertebrata and invertebrata, as well as many of the 

 protozoa. We usually speak of the consumers as " animals." 



1 Science Progress^ October 1907. 



I 



