Cell-specific growth and cell-specific production estimates of phytopl
ankton have been calculated in the past by a simple exponential model
(constant uptake-division) that describes the time rate change of carb
on, C, and assumes both continuous division and continuous uptake. We
propose three new models (variable uptake-division, variable uptake-c
onstant division, and diurnal) for making more accurate estimates of t
he algal growth rate, mu. The variable uptake-division model is the mo
st complex and requires species-specific information on the division p
attern. The diurnal model can provide accurate mu estimates while requ
iring only two measurements of C and no other parameters, but it requ
ires 48-h incubation times. The variable uptake division and variable
uptake-constant division models require additional work compared to th
e constant uptake-division model, but the effort mis warranted because
they also provide a direct approach for quantifying the dependence of
mu on the photoperiod and thus enable greater confidence in applying
mu to ecological studies, in which the light climate may differ from t
hat of the experiment.