210 BULLETIN OF THE BUREAU OF FISHERIES. 



tions on the metabolism of several marine animals showed that it would be impossible 

 for the plankton organisms that could be consumed to provide the required amount of 

 carbon or nitrogen. He found surprisingly large amounts of organic matter dissolved 

 in the sea water. His results have been checked up by Raben (1915), who found an 

 average of 12.25 mg- of organic combined carbon per liter in the Bay of Kiel, while in 

 water from the Baltic it amounted to 3 mg. per liter. Compared with the amount of 

 organic substance present in the form of living organisms, these results are very high. 

 The total amount of the organic combined carbon in the plankton at Laboe in Kiel 

 Bay was found by Lohman (1908) to vary between 12.7 and 189.8 mg. per 1,000 1. of 

 sea water. As an estimate of the maximum amount of organic matter in the form of 

 plankton that may be found in the ocean, we may refer to the phenomenal haul made in 

 the Bay of Kiel referred to by Brandt (1898), which contained 0.19 mg. of protein, 

 0.05 mg. of fat, o.43.mg. of carbohydrate, or a total of 0.67 mg. per liter. Raben (1905)! 

 who analyzed water from the same vicinity, found the mean value of organic combined 

 carbon in dissolved form to be 12,250 mg. per 1,000 1., or about 60 times as much as 

 that ordinarily present in the form of plankton organisms and nearly 20 times as much 

 as that present in the plankton when at its maximum. Putter's view is that the plank- 

 ton organisms are only of secondary importance in the nutrition of marine animals, 

 just as insects are to insectivorous plants which depend primarily on the photosynthesis 

 of starch to supply their needs. The facts presented by Putter present some ground 

 for his hypothesis, but the actual utilization of these dissolved organic compounds as 

 food by marine animals remains undemonstrated. 



Another great source of marine food supply has been suggested by Petersen (1890), 

 who expressed the idea that the abundance of fish on the Danish coasts was due chiefly 

 to Zostera, which is better known to fishermen as eelgrass. Petersen and Jensen (191 1) 

 tried to show that, in all probability, the plants of the eelgrass belt and not the plankton 

 organisms should be regarded as the main sources of the organic matter of the sea bottom 

 in Danish waters. Their reasoning is based on the fact that the quantity of carbon in a 

 series of bottom samples is directly proportional to the amount of Zostera vegetation 

 and not to the quantity of plankton present. 



The study was continued in greater detail and published by Jensen in 1914. He 

 showed that the eelgrass plays an important part in the production of organic matter in 

 the sea. In all the Danish waters he found fragments of eelgrass deposited in greater or 

 less quantities, for the most part in very fine particles as detritus. In this detritus he 

 found comparatively few diatom shells. Much of the detritus particles were too small 

 to be identified by the microscope as of eelgrass or plankton origin. By chemical means, 

 however, Jensen was able to determine the source of the organic matter in the sea bottom. 

 He found that the eelgrass cells contain a considerable quantity of starchlike substances 

 known to the chemists as pentosans, whereas those of diatoms are composed mainly of 

 silica and those of peridineans of fairly pure cellulose. By comparing analyses of various 

 bottom samples of organic matter with those of eelgrass and diatoms the following con- 

 clusions were reached : 



(1) In the more sheltered waters the organic matter of the sea bottom is to a preeminent degree 

 formed by eelgrass. 12) In the more open waters, at least half of the organic matter is probably formed 

 by eelgrass. ( 3 ) In the deepest waters the organic matter is probably formed chiefly by the plank- 

 ton organisms. 



