Biological Availability of Soluble Reactive Phosphorus in Anoxic and Oxic Freshwaters

Abstract

The availability of hypolimnetic phosphorus was assessed by a short-term bioassay, based on ³²P uptake kinetics. In the anoxic hypolimnia of eight lakes and in anoxic model systems (core tubes), at least 80% of soluble reactive phosphorus is biologically available. However, biologically available phosphorus is only a small fraction of soluble reactive phosphorus in iron-rich, previously anoxic waters after aeration and in lake water from the anoxic–oxic interface. This result is supported by published data for oxic waters from epilimnia of lakes, rivers, sewage effluent, and precipitation.