Do small swimmers mix the ocean?

TL;DR

This paper investigates how small marine organisms, through their locomotion, contribute to ocean mixing by analyzing hydrodynamic mechanisms and comparing their impact to turbulence, highlighting their significant role in biogenic mixing.

Contribution

The study introduces a hydrodynamic model of small organism locomotion-driven drift and evaluates its effectiveness in ocean mixing compared to turbulence.

Findings

Small organisms like krill and jellyfish can significantly contribute to ocean mixing.

Locomotion gait influences the effectiveness of biogenic mixing.

Biogenic mixing by small drifters can be substantial relative to turbulence.

Abstract

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.