Metabolic indicators for phosphorus limitation

Summary

Phosphate turnover time is a function of three different variables: phosphate concentration, biomass, and phosphorus stored within the cells. The integration of these three factors makes phosphate turnover time a particularly good indicator for estimating phosphate deficiency by lake plankton. The organisms responsible for the phosphate uptake are not entirely the same as those responsible for photosynthesis. Seasonal patterns of the size distribution of the plankton responsible for the uptake of radioactive phosphate showed that only under phosphate enrichment or during periods when phosphate was not deficient did the size distribution approach that for carbon uptake. Some important survival strategies emerge from this observation. Small cells have a greater affinity for phosphate but cannot store phosphate as well as larger cells. When exposed to high phosphate concentrations or intermittent inputs of phosphate, larger cells tend to have a competitive advantage.