PHOSPHORUS UPTAKE AND GROWTH-KINETICS OF 2 PLANKTONIC DESMID SPECIES

Phosphorus (P) uptake and growth kinetics under continuous P limitatio n in chemostat culture were studied in two planktonic desmid species: Cosmarium abbreviatum originating from an oligo-mesotrophic lake, and Straurastrum pingue from a eutrophic lake. Under stringent P limitatio n (steady-state growth rates up to 0.015 h(-1)) C. abbreviatum showed a higher affinity for P uptake and for growth than S. pingue. This com petitive advantage over S. pingue disappeared when P limitation became less severe (growth rates above 0.015 h(-1)), due to a sharp decline in the affinity of C. abbreviatum for P. At all growth rates tested C. abbreviatum showed a higher biomass yield per unit of P than S. pingu e. As S. pingue had double the maximum growth rate of C. abbreviatum a nd displayed higher maximum P uptake rates, it is likely to be better adapted to a eutrophic, dynamic environment where P release is predomi nantly in pulses.