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Bedeutung sedimentstratigraphischer untersuchungen für die seentherapie

Hupfer M.

Studia Quaternaria

2004

Vol. 21

171-178

Sediment investigations in five different lakes were used to examine how in-lake measures to reduce eutrophication (chemical precipitation, aeration and capping) were recorded as historical events in the sediment stratigraphy. In retrospect, sediment records can be helpful tools for the evaluation of failures in the field of lake restoration. The single or repeated applications of aluminium salt in Lake Auensee and Lake Süsser See have shown a permanent enrichment of phosphorus in the respective horizons. Enhanced P retention was also observed after the application of iron salts in Lake Gross-Glienicker See. In that case, the permanent P fixation by iron in the sediment was probably supported by positive feedback mechanisms induced by a lower trophy state and a higher availability of Fe(III) hydroxides as electron acceptor for microbial mineralisation. On the basis of vertical profiles the additional P retention per area was quantified for use in a P balance. The effectiveness of chemical treatment and sediment capping depend on the deposition rate of new material above the artificial layer and its contribution to the total P release. The evaluation of finely resoluted sediment profiles demonstrated that no correlation between P release rates and the mobilisable P pool (and total P) should be expected. It was calculated that the phosphorus pool in the sediment of Lake Arendsee could sustain the observed high P release rates only over a period of three months. The study demonstrates that investigations of sediment stratigraphy are an important tool in the applied limnology to decrease the risk of failure before and to assess the efficiency after lake restoration measures.