BayCEER Workshop 2024

Comparative analysis of two eutrophic lake sediments treated with a CaO₂-based lake restoration agent

Eutrophication has become a global problem, mainly caused by anthropogenic influences and climate change. Eutrophication describes the drastic shift of an aquatic ecosystem from a healthy and diverse macrophyte-dominated to a phytoplankton-dominated state characterized by algal blooms and decreasing biodiversity. Consequent elevated water turbidity and oxygen (O₂) depletion cause aquatic plants and animals to die off. Therefore, the water body loses its ecological function and becomes unusable for recreational and commercial purposes. Especially small and shallow lakes are highly vulnerable to eutrophication, making it a contemporary problem for many cities and towns. 

Lake restoration approaches are numerous, often expensive and ecologically destructive. A relatively cheap and gentle method is calcium peroxide (CaO₂), which slowly releases O₂ when dissociating in water. In theory, this should promote aerobic microbial organic matter degradation, while released calcium ions precipitate bio-available phosphate. However, the mechanisms of CaO₂ as a lake restoration agent are still poorly understood.  

In this experiment, the impact of a CaO₂-based lake restoration agent (CLRA) on two eutrophic lake sediments is analyzed via microcosm incubations under both oxic and anoxic conditions. The experiment was performed with a commercially available CLRA over an incubation time of approx. 13 weeks. The release of CO₂ and CH₄, as well as O₂ consumption in the microcosms, were measured using gas chromatography. The concentration of relevant nutrients (e.g. NH₄⁺, NO_x^-, and PO₄^3-) was determined with colorimetric assays. Surprisingly, the two sediments responded distinctly to the CLRA. While one sediment responded with increased CO₂ emission, the other had lower CO₂ production rates, indicating changes in microbial activity. Currently, 16S rRNA gene amplicon sequencing data is being analyzed to identify enriched members of the prokaryotic community driven by CLRA application.