From 1991 till 2000 I worked with Peter Coesel on the ecophysiology of planktonic desmids. During my Ph.D. we described that 2 species, of approximately the same size, had different inorganic phosphate uptake kinetics that could explain their ecological distribution. Staurastrum chaetoceras, a species from eutrophic lakes, had a higher maximum (P)-uptake rate and higher maximum growth rate. Cosmarium abbreviatum, a species typical of oligo-mesotrophic lakes, had a higher affinity for P-uptake and a higher P-storage capacity. During my Post-Doc period we could show that desmids do not rely on diffusive CO2 acquisition and that some species have high affinity HCO3 - uptake kinetics. In general, species from weakly buffered waters cannot use HCO3 - , but the pH of the water is likely not the major factor underlying desmid ecological distribution.