THE ROLE OF PROTOZOAN COMMUNITIES IN FRESH-WATER AND SOIL ECOSYSTEMS

A selection of production values for testacean and ciliate communities in lakes, streams, mosses and soils is quoted. Two energy budgets for protozoan communities in the field are constructed using ecological efficiences. For the given habitats, protozoan production is compared with that of metazoa. In many ecosystems, protozoa are second only to bacteria in terms of biomass turnover. The main factor controlling production is the distribution of mortality over a growth period, with a number of morphological and behavioural strategies also being important. Nutrients accumulated by protozoa are released soon after their death, making then available again for the bacteria. Decomposition times of the shells of shelled protozoa depend on environmental factors and can be used as an indicator of microbial activity.