ciated with seston increase to 0.15 mg O^/mg of oganic matter/day. It 

 appears that the metabolic activity of river seston is higher than that 

 of the lakes. 



The photosynthetic activity of phytoplankton is an important 

 component ofthe living fraction of seston. It depends on the quality of 

 water, and may be used as an index of pollution. Under the influence of 

 moderatepollution by nontoxic wastes, photosynthesis in the zone of 

 pollution rises, apparently at the expense of enrichment of the water in 

 nutrients. The Neman River graphically demonstrates this reaction in 

 response to an influx of sewage (Figure 4). Below the inflow, 

 photosynthesis increased by three fold. Depending on the intensity and 

 character of pollution, photosynthesis either increase or decrease 

 markedly. In all cases, a notable deviation of photosynthetic activity 

 from the average level characteristic of clean waters is observed in the 

 polluted zone, it should also be noted that such generally accepted 

 indices as oxygen consumption is more highly variable than photosynthetic 

 activity, and yields less precise results when pollution levels are low. 



0.6 



12 34 5 6 



7 8 9 



STATION 



10 11 12 



Figure 4. Relationship of photosynthesis ($) and distruction (D) 

 the Neman River in August of 1975. 



in 



155 



