  In this communication we address some hydrodynamic aspects of recently
revisited drift mechanism of biogenic mixing in the ocean (Katija and Dabiri,
Nature vol. 460, pp. 624-626, 2009). The relevance of the locomotion gait at
various spatial scales with respect to the drift is discussed. A hydrodynamic
scenario of the drift based on unsteady inertial propulsion, typical for most
small marine organisms, is proposed. We estimate its effectiveness by taking
into account interaction of a swimmer with the turbulent marine environment.
Simple scaling arguments are derived to estimate the comparative role of
drift-powered mixing with respect to the turbulence. The analysis indicates
substantial biomixing effected by relatively small but numerous drifters, such
as krill or jellyfish.
