Prospects of damaged calcareous spring systems in temperate Europe: Can we restore travertine-marl deposition?

Calcareous mires are peat forming systems fed by calcareous groundwater that regularly deposit travertine (CaCO3) on the soil surface or in small pools that are present in such mires. At present almost all calcareous mires in Poland are degraded, most often by land use, which has led to disturbances in local hydrological systems. An experiment was set up in a degraded spring mire in western Poland to test if travertine deposition could be restored. Trees were removed to increase surface water temperatures, and a system of open water pools was constructed to measure CaCO3 deposition in the surface water. We also studied three references systems with active CaCO3 deposition in Poland and in Latvia. The pools in the restoration site in Poland showed very little CaCO3 deposition (less than 0.2 μg · cm−2 · d−1), while the Polish reference site had significantly higher, but still modest, rates of CaCO3 deposition (ca 0.8 μg · cm−2 · d−1). At the reference sites in Latvia, we measured considerable CaCO3 deposition (up to 8 μg · cm−2 · d−1). Five years after the restoration measures in the Polish restoration site had been carried out, the vegetation showed little resemblance to the vegetation in spring systems with active calcite deposition in Poland and Latvia. Water analyses showed that the water in our restoration project was not supersaturated by calcite and had very low CO2 concentrations compared to the reference areas. The CO2 concentrations in the pool seemed a good predictor for CaCO3 deposition, better than Ca2+ concentrations. Changes in ground water flows in the source area could have been responsible for the loss of supersaturated groundwater at our restoration site. Our study showed that efforts to restore former calcareous mires can be frustrated when groundwater flow paths have been altered.