SECT. 2 J PRODUCTIVITY, DEFINITION AND MEASUREMENT 131 



Table I 



The Vertical Distribution of Phytoplankton (Coccolithophorides, Diatoms, 

 Dinofiagellates) in the Central Minimum Area of the South Atlantic. [According 

 to Steemann Nielsen and Aabye Jensen, 1957 (calculated after Hentschel)] 



Table II 



Vertical Distribution of Chlorophyll in the Lake Wesslingsee (5 August, 1948). 

 Depth of photic layer (according to the vertical distribution of oxygen) was 



about 2.5 m (Gessner, 1949) 



Chlorophyll in the photic layer, 75 mg/m 2 . 

 Chlorophyll below the photic layer 485 mg/m 2 . 



photic zone (see Table II). Of course all of the algae are produced in the photic 

 zone, but they sink passively to the bottom, where they settle, die and become 

 partly decomposed. The herbivorous zooplankton is unable to reduce effectively 

 the sinking masses of algae by grazing. In all probability the duration of the 

 sinking of a single alga is too short owing to the small depth. Thus an organic 

 sediment is formed by means of the partly decomposed plankton algae. This 

 type of locality might be characterized as an inharmonious biotype. A material 

 part of the primary production — in many cases probably the main part by far 

 — never reaches the next ordinary trophic level, the herbivores, but is lost as 



