Deep-sea hydrothermal vent communities are characterized by complicated taxonomic, trophic, and spatial structure. Different animals consume chemosynthetic bacterial production to a variable extent and by different ways. Different animal groups demonstrate variable degree of adaptations to the extreme environment of hydrothermal vent systems. According to their ecological requirements, vent animal populations occupy different zones within the vent field. The boundaries of different vent fauna assemblages could be rather sharp or feebly marked appearing to be defined by gradients of water chemistry as well as the hydrodynamic regime within the vent field. To ensure the correct analyses of bioconcentration function (BCF) of vent organisms, such factors as taxonomic position, trophic specialization, patterns of physiology, ontogenetic stages, and spatial disposition of animal population within the vent field should be taken into consideration.