Impacts of an Oxygen Slow-Releasing Calcium Peroxide Formulation on Oxygen Availability and Microbiota in Sediments of a Shallow Eutrophic Lake

Abstract Small lakes and ponds are often of critical ecological and economic importance. At the same time, they are increasingly impacted by anthropogenic activities, leading to eutrophic or hypertrophic conditions. These are typically accompanied by increasing primary production, nutrient, and detritus accumulation. Owners and stakeholders are often challenged to decide on feasible and appropriate measures for lake restoration. Addressing one of these measures, this study explores passive sediment aeration through oxygen slow-release from a calcium peroxide (CaO 2 ) formulation amended at the sediment surface. Compared to other peroxides, CaO 2 has a slow dissociation rate, which may enhance organic matter degradation and microbial activities over months. This study investigates the application of a CaO 2 -based lake restoration agent (CLRA) by a fine-scale dissection of its application to an eutrophic lake sediment. Using laboratory sediment columns, a dose–response approach, fine-scale microsensor analytics, and 16S rRNA gene amplicon sequencing, we provide evidence for an increased oxygen availability within sediments while other biogeochemical parameters remained unaffected. Significant impacts on sediment height were not detected, and microbial diversity remained stable across depths and CLRA dosages. However, characteristic shifts in microbial communities in upper sediments, specifically within aerobic heterotrophs and carbohydrate-degrading taxa within the Gammaproteobacteria, Bacterioidota and others were clearly detected. The findings provide first detailed insights into the sedimentary and microbiological impacts of a CaO 2 formulation applied in lake restoration. Better understanding the mechanisms and ecosystem impacts of CLRA applications will be vital for the implementation of effective and ecologically sound lake restoration strategies. Graphical Abstract