Bioavailability of sedimentary phosphorus under repeated sediment resuspension with the addition of algae.

The bioavailability of sedimentary P was investigated under repeated sediment resuspension with and without the addition of algae. Results show that the release of P as dissolved total P and dissolved inorganic P depends on the reduction in Fe/Al-P and Ca-P in the sediments. The reduction rates can be attributed to sediment resuspension and algal assimilation. However, under a low algal concentration, the assimilation of algae in P is lower than the readsorption of reoxidized Fe or other P-binding matter, such as clays and CaCO3 particles. This result was confirmed by the increase in algal available P (AAP) under sediment resuspension conditions with and without the addition of algae. Although measuring the formation and reduction rates of AAP is difficult, AAP is a good predictor of the bioavailability of sedimentary P. The bioavailable P in the sediments can be estimated using the sum of NH4Cl-P, AAP, and %Ca-P at certain concentrations of algae given the assimilation of Ca-P under sediment resuspension conditions with the addition of algae.