THE DENSITY OF ANIMALS ON THE OCEAN FLOOR 



199 



The contents of a sec- 

 tion ojf the southern 

 part of the West Af- 

 rican coast. The quan- 

 tity of animal life is 

 greatest at 40-50 

 metres. 



The result of our investigations in this field, therefore, is that on the 

 ocean floor there are about 10 animals per square metre with a total 

 weight of about one gram. This is an astonishingly large figure consider- 

 ing that at a depth of a few hundred metres in Northern European and 

 Mediterranean waters there are only a few grams of animals per square 

 metre. This surprising density right down to between 5,000 and 8,000 

 metres suggests that food conditions in the abyss are not so poor as we 

 have been inclined to think, and this in turn leads us to suppose that 

 abyssal water currents must be stronger than formerly believed. 



Although the relatively small number of samples so far obtained from 

 the extreme depths will not allow of any comparison, or of the establish- 

 ment of animal communities, there do seem to be certain variations corre- 

 sponding to what we might expect. The deep samples taken off the south- 

 west of Africa averaged 0.5 gram, off the Congo 0.37 gram, and off East 

 Africa 0.2 gram. This agrees very well with the fact that food production 

 is best off South-west Africa and poorer in the tropical Atlantic and the 

 Indian Ocean. It is also very natural that the Banda Sea, an inland sea 

 between the Moluccas and the small Sunda Islands, yielded strikingly 

 rich samples, appreciably richer than the open ocean. 



In addition to the deep-sea samples referred to, we used the Petersen 

 grab for obtaining a considerable number of samples in shallower water, 

 usually sectionally; that is to say, we took a series of samples extending 

 from well inshore ( 10 — 20 metres) out to the deep sea. Sections were thus 

 sampled off the west and east coasts of Africa, in the Bay of Bengal, in 

 the Gulf of Siam, in Milford Sound, New Zealand, off Campbell Island, 



