Abstract
Cell-specific growth and cell-specific production estimates of phytoplankton have been calculated in the past by a simple exponential model (constant uptake-division) that describes the time rate of change of carbon, C*, and assumes both continuous division and continuous carbon uptake. We propose three new models (variable uptake-division, variable uptake-constant division, and diurnal) for making more accurate estimates of the algal growth rate, μ. The variable uptake-dividion model is the most complex and requires species-specific information on the division pattern, The diurnal model can provide accurate μ estimates while requiring only two measurements of C*and no other parameters, but it requires 48-h incubation times. The variable uptake-constant division model can also provide accurate μ estimates and can be applied to data with <24-h incubation times. The variable uptake-division and variable uptake-constant division models require additional work compared to the constant uptake-division model, but the effort is warranted because they also provide a direct approach for quantifying the dependence of μ on the photoperiod and thus enable greater confidence in applying μ to ecological studies, in which the light climate may differ from that of the experiment.