Potentially mobile phosphorus in Lake Erken sediment

The amount of potentially mobile phosphorus (P) in Lake Erken sediments was determined by P release experiments, and forms of mobile P were identified by P fractionation. Amounts and forms of this P were compared to P release d by sediment diagenesis. Calculated on the top 30 cm of a sediment core, t he amount of potentially mobile P was 5 g/m(2), consisting mainly of organi c-P (NaOH-nrP) but also of P associated to iron (BD-P). P release experimen ts were performed by maintaining steep diffusion gradients in Bow-through c hambers under oxic or anoxic conditions. Using this method it took no longe r than three weeks to release an amount of P from the main P mobile pools ( NaOH-nrP, BD-P) corresponding to P naturally lost during sediment diagenesi s, a process which normally takes years. Release rates as well as mobile am ounts of P in the NaOH-nrP pool varied significantly depending on the redox status. In conclusion, the release method applied made it possible to dete rmine potentially mobile P under specified conditions and to detect ecologi cally important P fractions in the surface sediments. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.