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Convection occurs in ice-covered lakes if solar radiation warms near-surface water from the freezing point towards the temperature of maximal density. One effect of convective mixing may be to suspend non-motile phytoplankton in the upper water column, providing cells with enough light for growth during ice-covered periods. Observations of the diatom Aulacoseira baicalensis under the ice cover of Lake Baikal, Siberia, support the hypothesis that convective mixing causes net suspension of cells. This paper presents a theoretical examination of the conditions under which convective flow fields can suspend algae in the photic zone of the upper water column. It is shown that the efficiency of algal suspension depends on the ratio of the still-water algal sinking rate, W_p, to convective updraft speed, W_u. The suspension efficiency is also shown to be affected by asymmetries in the flow field and night-time …