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We analyze the effect of the Basset history force on the sedimentation ofnearly neutrally buoyant particles, exemplified by marine snow, in athree-dimensional turbulent flow. Particles are characterized by Stokes numbersmuch smaller than unity, and still water settling velocities, measured in unitsof the Kolmogorov velocity, of order one. The presence of the history force inthe Maxey-Riley equation leads to individual trajectories which differ stronglyfrom the dynamics of both inertial particles without this force, and idealsettling tracers. When considering, however, a large ensemble of particles, thestatistical properties of all three dynamics become more similar. The maineffect of the history force is a rather slow, power-law type convergence to anasymptotic settling velocity of the center of mass, which is found numericallyto be the settling velocity in still fluid. The spatial extension of theensemble grows diffusively after an initial ballistic growth lasting up to ca.one large eddy turnover time. We demonstrate that the settling of the center ofmass for such light aggregates is best approximated by the settling dynamics instill fluid found with the history force, on top of which fluctuations appearwhich follow very closely those of the turbulent velocity field.

History effects in the sedimentation of light aerosols in turbulence: the case of marine snow