the specific composition, particularly of organisms of the first group, may 

 be of decisive significance. For direct consumption by man (commercial or- 

 ganisms), some organisms of the second functional group are of great 

 significance. 



Of the many hydrochemical components, substances defining the overall 

 characteristics of the water (carbonate system, relationship of calcium and 

 magnesium, sodium and calcium, chlorine and sulfate), as well as dissolved 

 organic matter and biogenic elements (nitrogen, phosphorus, iron) and micro- 

 elements (manganese, boron, copper, cobalt, etc.) are quite significant. To 

 this normal composition of natural water, we must now add chemical pollu- 

 tants, consisting of many different compounds, the chemical nature and 

 biologic activity of which are not fully known. We do not know in what form 

 they are present in the water and what are the paths of their transforma- 

 tion. We note that they always influence hydrobiologic processes in the 

 reservoir. As a rule, this influence is not desirable for man and his 

 activity. The aquatic organisms of each functional group have differing 

 sensitivities to the effects of toxic substances which, with pollution, 

 leads to restructuring of the specific composition within each group and 

 among species from various groups. Toxic substances, depending on their 

 chemical nature and concentration, suppress and reduce the population of 

 some species while others are stimulated and increase their numbers, while 

 still others are indifferent, i.e., retain their previous status (Stroganov 

 1978). 



A change of dominance (predominant species) may not change the quantita- 

 tive aspect of a functional group. It will play its role in the cycle of 

 matter in a reservoir. However in the formation of good water quality and 

 the creation of high productivity of commercial organisms, these changes in 

 hydrobiologic processes may be undesirable. Therefore, we must limit the 

 delivery of chemical pollutants to a body of water if we desire to use it 

 for fishing purposes or for the supply of drinking water. 



The interrelationships between functional groups in a reservoir can be 

 drawn in the form of a diagram (Figure 1). 



An actual body of water is an open system for both matter and energy. 

 Therefore, reducers must process not only the substances which are trans- 

 formed from primary organic matter by the producers, but also substances 

 which enter the body of water from without. Usually, as organic matter in 

 the water increases, the number of organisms which mineralize it also in- 

 creases, but this process always involves some delay. 



If we represent primary producers as P, all consumers and transformers 

 as C and reducers as R, in the ideal case P = C •»■ R. However, reducers can- 

 not mineralize all dissolved organic matter completely, and some of it falls 

 to the bottom sediment, while some remains in the dissolved state. Since 

 there are sediments accumulated in past eras in all reservoirs, we can con- 

 clude that reducers have never been capable of mineralizing all of the dead 

 organic matter in reservoirs. Consequently, the actual relationship has 

 been: P+A=C+R+0, orP+A=C+R+B+0, where P is the primary 

 organic matter of producers; A is that entering from without (allochthonic 



22 



