Bioavailability of Phosphorus Inputs to Lakes

Abstract Interpretation of the potential bioavailability of phosphorus forms and fractions indicates some of the P entering lakes may have a limited effect on lake productivity. Some P sources, such as land runoff, are often high in particulate P, significant portions of which cannot be utilized in the growth of algae and higher plants. Based on existing information (mostly from Great Lakes studies), potentially bioavailable P in tributaries generally does not exceed 60% of the total P and is often considerably less. Potentially bioavailable P is shown to correspond to the dissolved reactive P (DRP) plus the fraction of particulate inorganic P obtained by extraction with 0.1 N NaOH. Whether potentially bioavailable particulate P actually becomes available in a receiving water depends on factors such as the receiving‐water DRP concentration and the position (location) of the particle in the water. A mathematical model, combining two classical modeling approaches, is used to illustrate the importance of positional limitation. Consideration of bioavailability in eutrophication‐control strategies should lead to more cost‐effective management.