BayCEER Workshop 2023

Calcium peroxide-induced elevated dissolved oxygen (eDO) for ecological lake restoration

Lake restoration enhances water quality in vulnerable ecosystems, often treasured by communities. Nutrient influx, e.g., from industry or agriculture, worsens the trophic state, especially in smaller lakes and ponds. Methods like dredging, common but costly and harmful, combat eutrophication. Calcium peroxide (CaO₂) emerges as a cost-effective, eco-friendly remediation agent that gradually releases oxygen at the sediment surface. CaO₂ dissociation elevates dissolved oxygen (eDO), fostering aerobic organic matter degradation, and reduces harmful bacterial and algal blooms via P-elimination.

In this ZIM project, an industry-academia collaboration, factors impacting eDO-driven organic matter reduction in small lakes (<5 ha) in Bavaria and Saxony are examined. Though CaO₂ aids organic matter/pollutant breakdown, its biotic and abiotic effects remain unclear. In this project, several lakes have been selected for CaO₂ application in Northern Bavaria and Saxonia, accompanied by intensive monitoring of biotic and abiotic parameters. In parallel, microcosm incubations are set up to investigate CaO₂-induced effects via microsensor measurements, gas chromatography, and 16S rRNA gene amplicon sequencing. Preliminary experiments show deeper oxygen penetration with CaO₂, while microbial community composition remained mainly unchanged. Additionally, applying CaO₂ may stimulate microbial activity, indicated by increased carbon dioxide production in oxic microcosm incubations, while anoxic incubations should not have increased activity. Furthermore, the emission of greenhouse gases, i.e., methane and nitrous oxide, is tracked in our ongoing work. Ultimately, we aim to elucidate how CaO₂ influences both biotic and abiotic parameters in freshwater sediments in vitro and in situ. Results from this project will contribute to a better understanding of lake restoration measures via eDO as a non-destructive alternative to dredging.