This study explored how rice straw biochar impacts the ability of a common freshwater algae, Scenedesmus quadricauda, to accumulate and transform manganese (Mn). Mn pollution is a growing concern, and algae play a crucial role in its cycle. Biochar, obtained from sustainable biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More, is increasingly used in agricultural and water treatment applications, but its effect on algae-Mn interactions was unclear.

Key findings:

• Mn stress on algae: High Mn levels inhibited algae growth, but they also triggered Mn oxidation into less toxic forms, likely as a stress response.
• Biochar to the rescue: Adding rice straw biochar reduced Mn absorption by algae cells, while increasing extracellular Mn binding. This suggests biochar helps alleviate Mn stress without hindering Mn removal.
• Mn transformation: With biochar, more Mn was oxidized to the highly charged Mn(IV) form, potentially due to reduced stress on the algae, allowing them to devote more energy to oxidation.
• Overall: Biochar in moderate amounts promoted Mn accumulation by algaeand their oxidation activity, providing valuable insights into Mn bioconversion and the potential benefits of biochar in aquatic environments.

This study suggests that using biochar in algae-based Mn treatment systems could be a promising strategy. Biochar can help algae cope with Mn stress while still effectively removing the metal from the water. Further research is needed to optimize biochar application and understand its long-term impacts on aquatic ecosystems.