The structure, i.e., regularity, is characterized by the presence of a 

 reserve of negative entropy. "Destructuring" indicates the development of 

 processes of entropy, a movement in the direction of "chaos" (Hilmy 1968). 

 This is a physical indication of the process promoted by the influence of 

 toxicants in ecosystem. However, as it was previously noted, the system as 

 a whole is a complex of factors, among which microorganisms and Protozoa 

 play a chief role to counteract entropy (Kamshilov 1973; Braginsky 1975; 

 Geptner 1977). The toxicant is "dispersed" in ecosystem and under the in- 

 fluence of microorganisms its concentration decreases. In the end, it 

 determines ecosystem buffering, its ability to consume and transform a cer- 

 tain quantity of toxicant (Kamshilov 1973). 



Buffering may be considered the degree of negative entropy of the system 

 as a major factor of preservation of its normal life. The transition to 

 "pathology" begins when the buffering limit is reached, and the system is 

 unable to withstand this toxic effect. 



Now we approach the main question of the problem of clean water: what 

 is a "pathological" waterbody or ecosystem, and how does it differ from a 

 "normal" one? In the light of the previous discussion, it appears as if the 

 answer should be: an ecosystem in a "pathological" state is a body of 

 water with a disturbed buffer system, in which the detoxification potential 

 is suppressed and negative entropy processes yield to the entropic pro- 

 cesses, i.e., degradational ones. 



One of the manifestations of such a state is an increased mortality 

 within community populations, particularly among highly organized life 

 forms; differing, as a rule, by a greater tolerance to toxicants. As a re- 

 sult of the increased death rate, population dynamics, age and sex ratio 

 changes, community structure changes correspondingly, and the system shifts 

 to a qualitatively different state. This state may be rather stable, parti- 

 cularly if the population which is resistant to toxicants becomes predomi- 

 nant, or unstable, with the tendency to further degradation, if this popula- 

 tion also is rather tolerant to toxicants. In certain individuals (as in 

 the intermediate stage between the normal state and death) various patho- 

 logical disturbances appear, which may be considered indicative of unfavor- 

 able conditions in the system. Symptoms may include disturbances in enzyme 

 systems and other biochemical changes corresponding functional disturbances, 

 structural pathohistological changes, alterations of conditioned reflex 

 activity, and behavioral reactions studied by toxicologists on the organism 

 and suborganism levels. 



Recently, it is difficult to tell what relationship exists between dis- 

 turbance of various functions and the structure of some organisms, including 

 fish. Of particular concern are the lethal concentrations of toxicants and 

 their threat to aquatic life at supra-organism levels. Critical, then, is 

 the extent that clear and evident pathological changes at organism level re- 

 flect the "pathology" of supra-organism level, i.e., the community or the 

 ecosystem, since every lower level of organization is less resistant to 

 toxic factors than the next higher one, and the ecosystem is in danger of 

 catastrophe only when all of the buffer systems at lower levels are des- 

 troyed. 



41 



