Variability in sinking rate of the freshwater diatom Asterionella formosa: the influence of colony morphology

Abstract

The sinking rates of colonies of a laboratory strain of Asterionella formosa were measured over a 5-year period, during which time mean cell length and cell volume reduced by almost an order of magnitude and the typical, stellate arrangement of eight-celled colonies was eventually lost. Changes in the sinking rates were not correlated with systematic changes in cell size and density but altered abruptly with the loss of the typical stellate configuration of the colony. Determination of the components of Stokes' equation showed that inert properties of individual cells have less influence upon the suspension of Asterionella than does the morphology of the colony itself.