stances and protein in fish drops and nitrogen consumption is reduced. The 

 expenditure of nitrogen for energetic processes increases (Table 1). 



Considering that the most evident negative deviations from the control 

 are observed in fish in concentrations of 0.30 g/liter, this quantity of 

 algae may be considered a threshold concentration. 



Lethal concentrations of blue-green algae caused more significant 

 changes in the biochemical composition and the fish metabolism. The data 

 show that fish lost dry and organic substances, protein and lipids. The 

 nitrogen balance was negative. Respiration intensified at a stage of 

 heightened movement activity and slowed down before death. A change in the 

 content of free amino acids (Table 2) and protein hydrolysates amino acids, 

 and also transaminase activity, pointed to the protein synthesis disturb- 

 ance. A decrease in nicotinamide coenzyme oxidized forms confirmed that 

 considerable changes in oxidation-reduction processes in tissues took place. 



Given the effect of the blue-green algae lethal quantities on fish, 

 changes in the thiaminase enzyme activity and total thiamine content 

 (vitamin B l ) were most significant. A thiaminase activity increase of 21- 

 40% in organs and tissues of fish influenced by the blue-green algae and 

 thiamine content drop of 38-50% in comparison with the control value, re- 

 sulted in a convulsion stage. A thiaminase activity increase of 28-55% and 

 a thiamine content drop of 49-74% caused the death of fish (Table 3). A 

 number of experiments, in which thiamine chloride injected at the initial 

 paralysis stage stopped the convulsions and prolonged the fishes' life, cor- 

 roborate that avitaminosis B , given the influence of lethal concentrations 

 of blue-green algae, is the reason for the fishes' death. This is also in- 

 directly confirmed by the fact that thiaminase activity in fish in natural 

 conditions (ponds, reservoirs) during the "bloom" period was heightened, 

 but the total thiamine content was lower than in autumn when no "blooms" 

 were observed (Table 4). 



A shortage of vitamin B 2 in organs of fish, given the influence of 

 lethal concentrations of blue-green algae, causes a disturbance in all meta- 

 bolism processes in which it participates. As mentioned above, in this 

 case the protein exchange, and likewise biosynthesis of lipid structure 

 compounds and normal transformation of substances in Krebs' cycle, are dis- 

 turbed. Changes in biochemical processes result in disturbances of some 

 functions. In particular, Bi-avitaminosis involves changes in the nervous 

 system's functional state. The latter is corroborated by a drop in the 

 cholinesterase activity in the fish's brain, given the influence of lethal 

 concentrations of blue-green algae. Some other symptoms typical of the 

 thiamine shortage are also observed in these fish, namely: Disturbance in 

 liver functions, the alimentary canal, and cardiovascular system; hemorrhage 

 in organs; and pathological changes in blood-formation. Blood analyses of 

 fish caught in waters covered with "bloom" areas support the latter 

 (Komarovskiy, 1970). 



Thus specific phenomena, e.g., Bj-avitaminosis , resulting in a number 

 of nonspecific changes--in particular, non-coordination of energetic and 



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