Figure 6
The various forces acting upon a cell of M. rubrum, to modify its position relative to the drifting sea ice. The relative motion between ice and water (Vrelative) creates a boundary layer where the laminar part has a velocity increasing linearly from zero at the surface while the turbulent part exhibits a logarithmic increase in relative velocity. M. rubrum is phototactic, swimming upwards to higher irradiance. (Vswim) Water column mixing can assist or counteract the upward movement. The skeletal layer formed at the bottom of growing sea ice consists of ice crystal lamellae interspersed by brine channels and tubes. Brine rejection compensated by inflowing seawater creates convection that may contribute to keep M. rubrum cells there. See discussion and Supplementary section 3 for details.
