information has shown, primary attention is given to the analysis of 

 normalcy and pathology at the organism and suborganism levels. Meanwhile, 

 aquatic life specificity lies in the fact that aquatic organisms live in 

 communities of different rank, and only their combined activity is of deci- 

 sive importance in the formation of those aquatic ecosystem characteristics 

 which are of interest to man, i.e., biological productivity and the 

 maintenance of proper water quality. 



Mass biological processes are of considerable importance for understand- 

 ing the processes of water quality formation. It is these processes which 

 lead to community structure transformation and the disturbance of balance in 

 ecosystems, i.e., the processes at the supra-organism level, which are ob- 

 jects of ecological/hydrobiological investigation, not the individual re- 

 sponses of organisms to a toxicant. 



A new trend in ecology, ecotoxicology, which has been recently 

 developed, and has already won world-wide recognition, deals not with the 

 individual organism response to toxic effects, but with the response of the 

 community and ecosystem, as well as the transformation of toxicants in 

 natural ecosystems. That is why it is necessary to understand the concepts 

 of normalcy and pathology at the supra-organism level of life organization. 

 What is a normal population? What is a population in the state of 

 "pathology"? What is a normal and a "pathological" biocenosis? What is a 

 "normal" and "unhealthy" ecosystem? Finally, what is an "unhealthy" body of 

 water, or "Krankenzee" described by German authors? 



It is not easy to answer these questions, especially considering the ex- 

 treme lack of knowledge of the consistencies of supra-organism system func- 

 tioning. At the same time, it is clear that analysis of this problem cannot 

 be guided by those initial concepts by which medicine, veterinary science 

 and ichthyopathology operate, since the processes taking place at the supra- 

 organism level are inadequate for the organism level processes. 



In this report the question of "normalcy" and "pathology" of the supra- 

 organism system is discussed from the points of view of demographic ecology 

 and synecology. 



POPULATION LEVEL 



One of the major criteria of conditions favorable to populations is the 

 ratio between birth and death. It is ^ery difficult to consider this factor 

 under natural conditions, but it may be characterized rather accurately in 

 experiments with synchronized test-cultures of short lived invertebrates. 

 In chronic toxicity tests with cultures of various Cladocera, after a series 

 of 5-6 generations a decline in fecundity of females as well as offspring 

 survival is observable. Similarly, an increase in mortality and a subse- 

 quent diminution of population can be noted. 



One of the "pathology" indices at the population level, which can well 

 estimate statistically and interpret graphically is the potential produc- 

 tivity value. This value is calculated by an equation, which connects the 



35 



