"lutea , Hydrocharis morsus - ranae , P olygonum amf ibium , Myriophyllum 

 verticillatum , Ceratophyllum submersum , Potamogeton lucens , and Potamogeton 

 perfoliatus . These qualitative characteristics are supported by the follow- 

 ing quantitative indices: Number of plankton alga species - 33; number of 

 higher water plant species - 22; number of groups of benthic organisms - 7; 

 number of phytoplankton organisms - 369 thousand cells/liter; number of 

 zooplankton organisms - 7 thousand specimen/m 3 ; number of Oligochaeta - 

 2280 specimen/m 2 ; relative number of Oligochaeta (per cent of the total 

 number of zoobenthos organisms) - 21%; mean protective covering of higher 

 water plants - 90%; biotic potential - 6 points; total number of bacteria - 

 3 million/ml; number of saprophitic bacteria - 3400/ml; number of spore- 

 forming bacteria in 1 ml - 10; ratio of the total number of bacteria to the 

 number of saprophitic bacteria - 900; and mg/liter of 2 demand for a 24-hr 

 period - 0.32. The toxicology investigations completed showed results 

 which did not differ from the control. 



Among the investigated sites, the greatest change in water quality is 

 observed directly below Moscow. In this region of the river, the negative 

 effect of water quality on all components of the ecological system is ob- 

 served; this effect is displayed in the decrease of species variety, in the 

 predominance of a-mesosaprobic organisms, low biotic potential, low P/R 

 ratios, and in the increase in the number of saprophitic bacteria. Higher 

 water plants are numerous here and Potamogeton pectinatus is the predomi- 

 nant species among them. Zoobenthos is composed of Oligochaeta , chirono- 

 mids, and leeches, and chironomids are represented by one species only. 

 Among plankton algae, Melosira granulata , Scenedesmus quadricauda , etc. 

 were encountered. Toxicological investigations allow us to ascertain 

 slight water toxicity. The following quantitative indices may illustrate 

 the above mentioned qualitative features: Number of plankton alga species - 

 10; number of species of higher water plants - 4; number of groups of zoo- 

 benthos organisms - 3; number of phytoplankton organisms - 178 thousand 

 cells/liter; number of zooplankton organisms - 31 thousand specimen/m 3 ; 

 number of Oligochaeta - 56,000 specimen/m 2 ; relative number of 01 igochaeta - 

 93%; mean protective covering of higher water plants - 20%; biotic potential 



- 2 points; total quantity of bacteria - 3.7 million/ml; number of sapro- 

 phitic bacteria - 30 thousand/ml; number of spore-forming bacteria in 1 ml 



- 200; ratio of the total number of bacteria to the number of saprophitic 

 bacteria - 120; and mg/liter of 2 demand for a 24-hr period - 0.96. 



The pollution level produced by such a large city as Moscow proved to 

 be so small due to the high effectiveness of treatment installations, so 

 that even a small river, such as the Moscow River, copes with pollution 

 rapidly. The rapid increase in water quality at sites mentioned below 

 verifies this fact. At the site 107 km from the mouth of the Moscow River, 

 significant indications of an increase in water quality in comparison with 

 a previous site are observed. This is also verified by the appearance of 

 B-mesosaprobic indicator organisms, an increase in both the number of or- 

 ganisms and their species variety. Coelastrum microporum and Closteium 

 lunula appeared among the phytoplankton. This site is characterized by the 

 following quantitative indices: Primary production - 0.52 mg 2 /liter for 

 a 24-hr period; demand - 1.71 mg 2 /liter for a 24-hr period; P/R ratio - 



33 



