# Calculated densities of marine phytoplankton cells

Range Table - link Various Richard W. Eppley, Robert W. Holmes and John D. H. Strickland, Sinking rates of marine phytoplankton measured with a fluorometer, J. exp. mar. Biol. Ecol., 1967, Vol. I, pp. 191-208 If ?c is the in situ density of a cell and ?s is density of the surrounding sea water the difference, ?, has been evaluated from the equation: pc-pS=?= 3K(v)t×?×d×p/Vg, where ? is in the units of g/cm^3 and (v)t is the terminal settling velocity of cells (cm/sec). d=the ‘nominal diameter’ of a cell given by 2(a×b×c)^0.333, where a, b and c are half the lengths of the three major axes (in cm). ?=the viscosity coefficient of sea water=1.08×10^-2g×cm^-1×sec^-1 at 20°C. g=the acceleration due to gravity=980cm/sec^2 and V=the volume of the cells in cm^3. K is a constant. For more details see page 198 The range of ?c for growing cells is 1.03-1.15g/cm^3 and for non growing cells it is 1.059-1.33g/cm^3. All objects the size of marine phytoplankton settling by a unit gravitational force in sea water will have a Reynolds number such that a Stokes-Law type equation will apply to their terminal velocity. It should, therefore, be possible to compute the in situ density differences between phytoplankton cells and the surrounding sea water (BNID 105169) from the measured mean settling velocities. Uri M 105168