effectiveness of utilization of sunlight in photosynthesis bend, we find 

 that its threshold intensity in oligotrophic and mesotrophic regions is 

 observed at the depth to which <1X of the subsurface radiation 

 penetrates, in eutrophic waters--about 10%. 



Data on the absolute effectiveness of utilization of solar energy 

 can be used to evaluate the radiocarbon method of measurement of primary 

 production. The maximum value of this effectiveness is about 20%. This 

 is the effectiveness which is observed at the bottom of the euphotic 

 layer. This means that the radiocarbon method, at least in the lower 

 portion of the layer of photosynthesis, provides quite realistic 

 results. 



A significant portion of the disagreement obtained in the study of 

 light as a factor in photosynthesis under laboratory and natural 

 conditions depends on the difference in the spectral composition of the 

 light. Due to chromatic adaptation, phytoplankton from the lower 

 portion of the photosynthetic layer has a set of pigments adapted to the 

 specific spectral composition of the penetrating radiation. This 

 phytoplankton, when placed in incubators with neutral-density light 

 filters, absorbs a much lower fraction of the radiant energy than in the 

 sea at the depth at which it lives. As a result, the threshold of 

 photosynthesis in incubators is observed at higher levels of irradiation 

 than jm situ^. The situation is somewhat 

 filters 



are used, but even in this case, 

 composition of the penetrating radiation 

 highly productive inshore waters. 



improved when blue light 

 the imitation of the spectral 

 is imperfect, particularly in 



Table 3. Kg (yg-atom N/£) for the rate of uptake of NO3 in cultures and 

 for the relationship of concentration of oxidized forms of nitrogen to 

 primary production, concentration of chlorophyll and AN. 



Objects studied 



Reference 



Cultures 



Small oceanic diatoms 



and coccolithophorids 



Neritic diatoms 



Neritic dinoflagellates 



Small flagellates 

 Natural populations of 



the tropics of the 



Pacific, Indian and 



Atlantic Oceans 



Tropic and temperate 

 zones of the ocean, 



20-30°C 



Rate of uptake 



0.1- 0.7 

 0.4- 5.1 

 3.8-10.3 

 0.1- 0.4 

 Relationship of nitrates 

 to primary production 

 At surface 3.33 

 At optimum AN level 2.56 

 Relationship of nitrates 

 to chlorophyll at opti- 

 mum AN level 4.2 

 Relationship of nitrates 

 to optimal AN 0.17 



Eppley et al 



1969 



Our data 



Vedernikov, 1976b 



254 



