CH. IX] 



THE PRODUCTIVITV OF THE SEA 



189 



was, at the least, 114 grams per square metre per year and the 

 approximation of these results is interesting. 



The composition of marine products. I have used the 

 terms " dry organic substance," " mussel flesh," " fish flesh," &c. 

 Now in any consideration of the productivity of a sea area, it 

 is necessary to compare the quantities of organic substances with 

 each other, and with corresponding land organic products. That 

 is, we wish to know what is the composition of such marine 

 " crops " as plankton of different kinds, fish, and other marine 

 flesh, &c. Brandt^ in 1898 made a number of such determinations 

 of the chemical composition of the plankton and I quote some 

 of his more important results here. Catches were made with 

 a quantitative plankton net, so that it was possible to estimate the 

 numbers of organisms present per unit volume of sea water. 

 These catches were then subjected to quantitative chemical 

 analysis. Some catches consisted predominantly of diatoms, 

 others of peridinians, and other? again of copepods. Thus it 

 was possible to obtain values for the chemical composition of 

 the principal planktonic constituents. Mixed plankton catches, 

 characteristic of different seasons, were also analysed, so that 

 the composition of the " meadows of the sea " could be compared 

 with that of land crops. All Brandt's results were obtained from 

 the examination of the plankton of Kiel Bay. 



The following table gives the percentage composition of the 

 dry substance of plankton and of various planktonic organisms : — 



For comparison with these figures I quote the composition 

 of various land crops-. 



1 Brandt, " Beitr. chemisch. Zusammensetzung Planktons," Wiss. Meeresunt. 

 Kiel. Komm. Bd. iii. Abth. Kiel, 1898. 



2 Ibid. 



