Likely controls on dissolved reactive phosphorus concentrations in baseflow of an agricultural stream.

High baseflow phosphorus (P) concentrations increase the likelihood of periphyton blooms. Several physical and chemical factors can control baseflow P concentrations such as hydraulic exchange with groundwater, particle size-sorting, redox chemistry and different sediment sources. We hypothesized that of these sources, anoxic sediments would allow P-rich groundwater to influence baseflow P concentrations the most and that the measurement of the equilibrium P concentration (EPC0) of sediments under oxic conditions would not predict P release in anaerobic sediment or baseflow P concentrations.