182 American Fisheries Society 



chiefly to Zostera which is better known to fishermen 

 as "eel grass." Petersen and Jensen (1911) tried to 

 show that, in all probability, the plants of the eel grass 

 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. 



This study was continued in greater detail and pub- 

 lished by Jensen in 1914. He shows that the eel grass 

 plays an important part in the production of organic 

 matter in the sea. In all the Danish waters he found 

 fragments of eel grass deposited in greater or less quan- 

 tities, 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 eel grass or plank- 

 ton origin. By chemical means, however, Jensen was 

 able to determine the source of the organic matter in 

 the sea bottom. He found that the eel grass cells con- 

 tain a considerable quantity of starch-like substances 

 known to the chemists as pentosans, whereas those of 

 diatoms are composed mainly of silica and those of Peri- 

 dineans of fairly pure cellulose. By comparing analyses 

 of various bottom samples of organic matter with those 

 of eel grass and diatoms the following conclusions were 

 reached: "(1) In the more sheltered waters the organic 

 matter of the sea bottom is to a pre-eminent degree 

 formed by eel grass. (2) In the more open waters, at 

 least half of the organic matter is probably formed by 

 eel grass. (3) In the deepest waters the organic matter 

 is probably formed chiefly by the plankton organisms." 



Calculations on the production of phytoplankton 

 (minute floating plant life) and eel grass per square 

 meter have been attempted, but what has been done so 

 far approaches a mere approximation only. In regard 

 to the phytoplankton, Hensen (1887) figured that one 

 square meter of surface produces annually 15-18 grams 



