Sediment and pore water composition as a basis for the trophic evaluation of standing waters

Sediments and pore water samples from four reservoirs in eastern Germany with different trophic characteristics have been examined (Neunzehnhain I - oligotrophic; Muldenberg - oligotrophic, dystrophic; Saidenbach - mesotrophic; Quitzdorf - highly eutrophic). Several parameters were analyzed regarding the dependence on the trophic state and the possibility to use them for the trophic evaluation of standing waters. The strongest influence of the trophic state could be found in the case of the parameters SRP, alkalinity and ammonium in the pore water. For the dry sediment, it could be concluded that the most important factor affecting the trophic state is the ratios of Fe:P and ALP, which were summarized to a metal: phosphorus sum ratio (MPS) and showed a clear threshold value for the potential to immobilize phosphorus in the sediment. Also, with the P fractions of the sediment samples, differences between the trophic levels became evident. Higher percentages of the reductively soluble, iron-bound fraction and of the biogenic fraction occurred in the reservoirs with higher trophic state, while comparitively higher percentages of the stable aluminum-bound fraction could be measured in the reservoirs with lower trophic state.