The sediments and benthic-pelagic exchange in the shallow lake Muggelsee (Berlin, Germany)

The sediments and exchange processes of the shallow (mean depth 4.9 m), polymictic. eutrophic Muggelsee have been studied over more than 30 years. Here, previous results are summarised and completed by new data. Sediment analyses were used to identify changes in loadings and migration processes within the sediments of the 12 000 year old lake. The surficial oligohumic sediments are rich in Fe (8.8 +/- 1.9% DW) and in P (2.7 +/- 0.5 mg P g(-1) DW). Mass balances of P and Fe as well as sediment trap measurements and sinking velocity analyses showed that the retention of matter strongly varies within seasons and years. The lake amplifies the seasonal fluctuations of P in the River Spree system by a strong redox-controlled, benthic P-release in summer. Since 1988, P-release has exceeded retention so that the lake changed from a P-sink to a source. The retention rate dropped in summer to -7.3 mg P m(-2)d(-1) and in winter to 1.4 mg P m(-2)d(-1).