Restoring eutrophicated lakes is vital for improving water quality in aquatic ecosystems often highly valued by local communities. Nutrient influx, mainly from changing land-use and agricultural runoff, exacerbates the trophic status, especially in smaller lakes. Traditional dredging, though prevalent, is expensive and environmentally harmful. An alternative approach uses water-insoluble calcium peroxide (CaO₂) for lake restoration, offering a cost-effective and less labor-intensive solution. CaO₂ slowly releases oxygen, increasing dissolved oxygen levels (eDO), promoting aerobic microbial degradation of organic matter in eutrophicated sediments. It may also mitigate harmful algal blooms through phosphorus elimination.

In this project funded within the "Water4All" ZIM network, several industry and university partners collaborate to analyze factors influencing organic matter degradation and sediment reduction in small lakes (2 amendment. Despite previous successful applications, uncertainties prevail about the specific biotic and abiotic factors affecting its efficacy. Several small lakes in Northern Bavaria and Saxonia were treated with CaO₂, with intensive monitoring of biotic and abiotic parameters. Concurrently, laboratory microcosm incubations are investigated for fine-scale assessment of CaO₂-induced effects through microsensor measurements and 16S rRNA gene amplicon sequencing.

Preliminary tests show increased levels of bioavailable O₂ in the sediment surface, showing a short-term increase in situ. Ongoing field data analysis will unveil further effects. In laboratory microcosms, intensive bioturbation of sediment columns observed even for unrealistically high CaO₂ dosage complicates biogeochemical data interpretation but alleviates concerns regarding ecotoxicological assessment. Amplicons for 16S rRNA gene sequencing are currently analyzed, to further examine the influence of CaO₂ amendment on sediment microbial community development. Taken together, the project aims to provide a comprehensive mechanistic and also freshwater ecology perspective of CaO₂-based treatment strategies for eutrophicated small lakes.