Longitudinal Gradients in the Chemical and Microbial Composition of the Bottom Sediment in a Channel Reservoir (Saidenbach R., Saxony)

Saidenbach Reservoir is situated in the Erzgebirge Hills, Saxony, in a catchment with agriculture as the principal use and a high sensitivity to soil erosion. The high elimination of total phosphorus (ca. 70%) mainly results from a) the sedimentation flux of planktonic diatoms and b) the adsorption to and sedimentation with mineral particles rich in iron. At stations with a high sulfide concentration in the 0–5 cm sediment layer (about 0.2%), the P content was likewise high (about 0.3%), probably due to the high iron concentration (more than 2.5% of dry weight). A fractionation procedure showed that the major part of the sediment phosphorus was not sensitive to reductants (dithionite) but has been found only in the following extraction step (NaOH extract).