VERTICAL-DISTRIBUTION OF PLANKTON ANIMALS IN THE NEAR-BOTTOM LAYER AND BIOLOGICAL STRUCTURE OF THE OCEAN

Among the species which have the greatest population density in the vicinity of the bottom there are obligatory and facultative dwellers of the near-bottom layer. The facultative dwellers are independent of the bottom media and their greatest population near-bottom density is a result of the contact between high population density pelagial layer and any bottom elevation. There is some symmetry in the vertical ranges of plankton species distribution from the surface downwards and from the bottom upwards. Even in the deep ocean some obligatory near-bottom species or their eggs and larvae can get the surface zone by means of turbulent diffusion or active movement and dispersion, and thus the near-bottom fauna has an impact on the whole water column population.