Impact of oxygen slow-releasing calcium peroxide on oxygen availability and microbiota in sediments of a shallow eutrophic lake

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 accompagnied by increasing primary production, nutrient and detritus accumulation. Owners and stakeholders are often challenged with a need for deciding on feasible and appropriate measures for lake restoration. Addressing these challenges, this study explores the use of passive aeration through oxygen (O2) slow-release from a calcium peroxide (CaO2) formulation amended at the sediment surface. Compared to other peroxides, CaO2 has a much slower dissociation rate, which may enhance microbial activities and organic matter degradation over longer time scales. This manuscript investigates the potential of CaO2 as a lake restoration agent by a fine-scale dissection of its application to a eutrophic lake sediment. Using replicated 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 and microbial diversity in treated sediments were not observed over a time course of two months. However, a shift in microbial community composition towards a higher relative abundance of typically aerobic lineages was clearly detected, while Cyanobacteria decreased in abundance. The findings provide primary insights into the sedimentary and microbiological impacts of a CaO2 formulation applied in lake restoration. Understanding the mechanisms and ecosystem impacts of such CaO2 applications are vital for the development of effective and ecological lake restoration strategies.