Xo. 55S 



NOTES AND LITERATURE 



381 



the coasts The result of these investigations is, therefore that 



the plants of the Zostera belt and not the plankton organisms 

 constitute the principal source of the organic matter in the 

 sea bottom." And this is in harmony with Petersen's conten- 

 tion that Zostera "is certainly the plant, which for a great part 

 conditions the fish-wealth of our coasts and attracts the fishes 

 from the open and deeper waters into the shallow, enclosed hays 

 and fjords." These are very important conclusions and de- 

 serve the careful consideration of students of marine animals in 

 other localities. These investigations may well serve as models 

 for investigators in many other regions, and this point of view 

 should also be applied to lakes and streams. 



When the black, foul-smelling bottom layer is examined it is 

 found to contain much methane or marsh gas. probably due to 

 the activity of bacteria, small amounts of oxygen and carbon 

 dioxide. The black color is mainly due to ferrous sulphiuV. 

 which in fresh water is mainly due to the reduction of sulphates 

 by anerobic bacteria. These black muds contain the greatest 

 amounts of organic materials. These soils are most abundant 

 in the inner fjords, and they represent an early stage of the 

 conditions, which in its extreme development is found in the 

 Black Sea. Jensen states that he does not know of a similar 

 condition of affairs in fresh water where he is inclined to think 

 such a condition is prevented by humic acid. This recalls the 

 phenomenon of "stagnation" which Whipple and others have 

 studied in American lakes, and which is even occasionally found 

 in rivers heavily charged with sewage. He concludes this chap- 

 ter with this striking sentence: "We may therefore, to a certain 

 extent, regard the large oceans as the lungs of the sea, which 

 supply the water-masses of the inner seas with oxygen and 

 remove the superfluous organic matter." 



Jensen next considers the transportation of the organic ma- 

 terials from its course near the shores to the bottom. The winds 

 are found to be an important agent in the process, as is shown 

 by the presence of a larger amount of debris in the water after 

 storms. By centrifuging this material is removed from the 

 water, and when examine.] mierosmpieally it is found to be 

 composed mostly of materials so finely divided that it is not pos- 

 sible to recognize its source. Examined chemically, as well as 

 microscopically, it is found to be "completely identical with the 

 uppermost brown layer on the sea bottom." 



