THE BARENTS SEA 



89 



reducing medium. The fauna of brown mud is usually very scarce, hence the 

 oxidizing medium is retained. The conditions under which the brown mud is 

 created are undoubtedly unfavourable for the growth of benthos ; Hessle has 

 also pointed this out in relation to the Gulf of Bothnia. The problems of 

 brown muds await further investigations. 



Plant foods in the sea-bed 



T. Gorshkova (1958) has analysed the organic matter present in the bot- 

 tom sediments of the Barents Sea. Their carbon content varies over all 



Fig. 29. Organic carbon content (A) and carbonates (B) in soils of Barents 

 Sea bottom (Gorshkova). 



A. 1 0-5%; 2 0-5 to 10%; 3 10 to 20%; 4 20 to 3-0%. 



B. I 0-25% 2 0-25 to 0-5%; 3 0-5 to 10%; 4 10% and more. 



from 0-15 to 3-12 per cent, that of nitrogen from 002 to 0-42 per cent, and the 

 ratio of the first to the second from 5 to 8-7 (average 7). These values are 

 close to those obtained for the shallow parts of the Atlantic Ocean. They 

 indicate the origin of the organic matter in sedimentation as mainly due to 

 plankton. The range of organic carbon in the upper layer of the Barents Sea 

 sediment is shown in Fig. 29. No simple relationship can be established be- 

 tween the bed's content of organic substances and some definite factor of the 

 media; it is found to be much too complex. 



The most constant relationship has been observed between the organic 

 matter content and the mechanical properties of marine sedimentation. As a 

 rule the larger the amount of the fine sediment fraction, the richer its organic 

 matter content (Fig. 30). This is clearly shown by a comparison of the organic 



