KINETICS OF LUXURY UPTAKE OF PHOSPHATE BY ALGAE-DOMINATED BENTHIC COMMUNITIES

The uptake of phosphate by benthic communities, dominated by living al gae, previously exposed to different levels of external nutrient loadi ng, exhibited first-order kinetics with respect to the intracellular P -deficit. This deficit is the difference between the maximum and the a ctual intracellular P-concentration. The maximum storage capacity of P per unit of dry weight was positively correlated to the level of exte rnal nutrient loading, whereas the phosphate uptake rate constant was negatively correlated. The observed internal P concentrations in the b enthic layer of test ditches over a period of two and a half years, in dicated a slight decrease towards a minimum value in a ditch with a lo w external P-input. In a medium loaded ditch the internal P-concentrat ion did not change significantly. In a high loaded ditch increasing in ternal P-concentrations over time were observed, towards P-saturation of the benthic community.