Calcium peroxide treatment of cyanobacterial blooms: Ecological safety assessment on submerged macrophyte Vallisneria natans.

Abstract

The outbreak of cyanobacterial blooms poses an increasingly serious ecological challenge. Our previous study found that calcium peroxide (CaO₂) has a high inhibitory effect on cyanobacteria, along with a practical application potential in cyanobacteria-dominated lakes. In order to explore the sensitivity of aquatic ecosystems to CaO₂ treatment, we conducted this study to elucidate the ecological impact of CaO₂ on Vallisneria natans (V. natans) when inhibiting cyanobacterial bloom. This study firstly optimized the performance of CaO₂ by preparing alginate-encapsulated CaO₂ (CaO₂-Bead), which prolonged the release time of reactive oxygen species (ROS). Subsequently, the sensitivity of submerged plant V. natans and its biofilm was explored. After adding 100 mg L^-1 CaO₂-Bead, significant inhibitory effect on cyanobacteria was found, and the inhibition rate of cyanobacterial biomass reached 93.5 %. More importantly, CaO₂-Bead can alleviate the oxidative stress, effects of Extracellular Polymeric Substances (EPS) structure and microbial community on the surface of leaf biofilm caused by cyanobacteria. At the same time, it decreased the damage of photosynthesis, mitochondrial transport, plant-pathogen interaction, mitogen-activated protein kinases (MAPK), and ubiquitin-mediated protein degradation in pathways in V. natans under inhibition of cyanobacteria. Our research provides a theoretical basis for evaluating the safety of CaO₂ on the aquatic environment when treating cyanobacterial blooms.