SIZE-DEPENDENT NITROGEN UPTAKE IN MICRO- AND MACROALGAE

The role of algal size as a controlling factor for nitrogen uptake kin etics is examined by comparing published values of N uptake rate and h alf-saturation constants in micro- and macroalgae. The uptake kinetics differ substantially among algae very different in size. Microalgae t ake up nitrogen much faster per unit of biomass than macroalgae at bot h high and low substrate concentrations, and microalgae have significa ntly higher affinity for nitrogen than macroalgae. These typical diffe rences in the uptake kinetics among small and large algae are commonly attributed to size-specific differences in the relative surface area (SA:V). Regression analysis demonstrates that size-specific variations in the kinetic parameters can be attributed to changes in relative su rface area over an extensive range of algal sizes, covering both micro - and macroalgae. These results agree with previously described relati onships between maximum uptake rate of nutrients (nitrogen and phospho rus) and SA:V within narrow size-ranges (either phytoplankton or macro algae), and emphasize the existence of a general coupling between phys iological and morphological properties in algae.