Transformation of phosphorus species in settling seston and during early sediment diagenesis

Sequential P extraction was combined with electron microscop and X-ray spectroscopy to characterise various P species and to study their transformation in settling seston and in recent sediment. During early diagenesis most of the particulate P formed in the water was redissolved. No net transformation into species that would resist dissolution was observed. It was shown that the phosphorus (P) content and the P flux of settling particles varied seasonally over one order of magnitude particles became enriched with reductant soluble P (BD-P) while settling through the hypolimnion changes in BD-P were highly significantly correlated with changes in reductant soluble iron (BD-Fe) bacteria oxidising Fe and Mn seemed to be mainly responsible for this increase in P concentration other fractions including organic P did not change during sedimentation most of the organic P and of the Fe bound P and 70 % of TP was released from the sediment during early diagenesis the sediment surface did not act as a trap for P migrating upwards from deeper sediment layers CaCO3 sedimentation contributed little to P sedimentation but significantly to the permanent burial of P.