Biohydrodynamics and Ecology of Life Forms of Pelagial

The relation between inertial forces and frictional forces characterizing the pattern of movement of plankton and nekton organisms, respectively, and expressed by the Reynolds number Re may be used as a base for classifying the life forms of the pelagial. The upper limit for the existence of euplanktic forms connected with devices for increasing the hydrodynamic resistance and ensuring passive floating with the least expenditure of energy corresponds to Re values ≦5,0 · 10⁵. The upper boundary of the nektoplankton is in correspondance to Re ≦2,0 · 10⁷. The organization of nekton organisms capable of active directed horizontal movement and with devices for reducing the hydrodynamic resistance is in accordance with Re >5,0 · 10³, as a rule is in accordance with Re > 10⁵.