Effect of hypolimnetic discharge on the faster deprivation of phosphorus from lake sediment (Lake Jabel, north-east Germany)
After the reduction in external phosphorus-load (P-load), in-lake measures became practicable for eutrophic Lake Jabel. The benthic release of phosphorus (P) was efficiently suppressed by a significant nitrate supply via its main tributary. The in-situ stimulation of P-release as a result of the temporary decrease in this nitrate load, and the simultaneous P-removal by deep-water siphoning and external P-elimination was primarily designed for the faster deprivation of P from lake sediment. This new strategy was aimed at exhausting the ‘P-surplus’, that is, the mobile redox-sensitive iron-bound P-portions of the uppermost sediment layers, where a re-supply from deeper layers is needed within the stratification period of 2 consecutive years of operation of the P-elimination system. By studying early benthic P-diagenesis it remains to be demonstrated whether this procedure can contribute to a re-availability of P-binding sites to guarantee the long-term effect of the measure.