Аннотация:he food spectrum of ciliates was investigated in different parts of the Chernaya River estuary (the White Sea) along salinity gradient (0-22%). Toward the river from the sea, the species structure became more simple, the ciliate density, percentage of raptorial feeders, and selectivity of food capture (for the whole ciliate community) decreased. The critical salinity level and high variation of environmental parameters are the main factors affecting the survival of ciliates and their food. Ciliates use a great part of the peridian production (daily elimination 20-80%) diatomean production to a lesser degree (daily elimination 0.1-0.3%). The rich and diverse ciliate community of the marine sites used food resources more completely than the more poor community of the river areas.