CALCULATION OF CELL-SPECIFIC GROWTH-RATES - A CLARIFICATION

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.