1062-3590/01/2801- $25.00 © 2001 MAIK “Nauka /Interperiodica” 0075 Biology Bulletin, Vol. 28, No. 1, 2001, pp. 75–83. Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2001, pp. 87–95. Original Russian Text Copyright © 2001 by Alimov. Studies on species diversity and its development and dynamics upon changes in environmental conditions are of great significance, because the risk of losing bio- logical diversity currently increases due to several fac- tors, including the necessity of utilizing the resources of natural ecosystems. One of the most important ques- tions addressed by biologists and ecologists concerns the number of species that can inhabit a limited area. Such studies on specific groups of aquatic organisms have been periodically performed for many years (e.g., Connor and McCoy, 1979, 1983; Dodson, 1991, 1992). Their results showed that the number of animal and plant species representing individual taxonomic groups has a tendency to increase with a decrease in the geo- graphic latitude and an increase in the water body area. Moreover, the relation between the number of species in these groups and water body area is described by an exponential equation. To solve many problems associ- ated with the analysis of biodiversity and specific fea- tures in the functioning of concrete ecosystems occupy- ing certain areas, it is important to estimate the number of species comprising these ecosystems and their con- stituent subsystems. This work deals with the effects of different factors on the number of aquatic species in water bodies that differ in type, size, and geographic location. The num- ber of species in ecosystems of water bodies depends on different factors, including the history of fauna for- mation. In addition, the key factors that can determine the possible number of species in each ecosystem include its territory (inhabited area) and trophic condi- tions. The former can be estimated from the area or vol- ume of the water body, and the latter, from the amount of primary production in it. Original and published data were used to estimate relationships between the number of species in the phyto- and zooplankton, macroflora, benthos, and ich- thyofauna, on one hand, and the area, volume, and pri- mary production of lakes, on the other. This analysis was performed for water bodies that differed in their type, origin, and geographic location. According to MacArthur’s theory of dynamic equilibrium, lake eco- systems were regarded as insular ecosystems. MATERIALS AND METHODS This work was based on the results of research per- formed by the Laboratory of Freshwater Hydrobiology (Zoological Institute, Russian Academy of Sciences), in which I have participated, including studies on northern lakes (Biologicheskaya produktivnost’ …, 1975), the Buryat Republic (Issledovanie vzaimosvyazi …, 1986), and southern Karelia (Reaktsiya ozernykh ekosistem …, 1997). A large amount of published data were analyzed. These were data on various lakes of the world (Stella and Margaritoria, 1966; Hobbie, 1973; Welch and Kalff, 1974; Ecology of Eutrophic …, 1979; Ecosys- tems of the World, 1984; Ecology of Oligotrophic …, 1992; Biodiversity of Shabla Lake …, 1998), including the lakes of Antarctica (Izaquirre et al., 1998), Belarus (Ekologicheskaya sistema …, 1985), the Baltic repub- lics (Reaktsiya ekosistem ozer …, 1983; Izmenenie struktury ekosistem …, 1988; Trifonova, 1990; Sostoy- anie myagkovodnykh ozer …, 1991), Siberia (Mosk- alenko and Votinsev, 1972; Putoranskaya ozernaya provintsiya, 1975; Ozera Khakasii, 1976; Biologi- cheskaya produktivnost’ pelagiali …, 1977; Lake Baikal …, 1984), Karelia (Biologicheskie resursy …, Studies on Biodiversity in the Plankton, Benthos, and Fish Communities, and the Ecosystems of Fresh Water Bodies Differing in Productivity A. F. Alimov Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Petersburg, 199034 Russia Received April 17, 2000 Abstract—The species diversity of phyto- and zooplankton, benthic animals, and ichthyofauna was studied in continental water bodies that differ in type, geographic location, size, and productivity. The results showed that the number of species in the communities of aquatic organisms and in ecosystems depends on the area and vol- ume of the water body and the level of plankton primary production. Corresponding relationships can be approximated by the equations of exponential and polymodal functions. The species number and biomass per unit area or volume proved to decrease as the area or volume of the water body increased. The greatest number of heterotrophic species was observed in water bodies whose primary production approached 1400 kcal/m 2 per year. It is proposed that the number of aquatic species in a body of water depends on the total area of the latter and the area of individual territories occupied by the representatives of certain species. ECOLOGY