Application of microalgae in remediation of heavy metal-contaminated soils and its stimulatory effect on wheat growth

Abstract

Heavy metal pollution has emerged as a significant threat to global soil environments, adversely impacting crop safety and human health. This study investigates the potential of microalgae as an environmental bioremediation tool and plant growth regulator. By examining the effects of four living microalgae species—Anabaena azotica, Anabaena variabilis, Chlorella vulgaris, and Scenedesmus obliquus—on cadmium (Cd) levels in soil and wheat, we assessed their ability to enhance soil fertility and promote wheat growth under varying cell number treatments. Our findings revealed that all four microalgae effectively reduced soil exchangeable Cd and limited Cd accumulation in wheat roots and stems. Remarkably, significant remediation effects were observed even at low-dose treatments, indicating that effective bioremediation does not solely rely on high concentrations. Additionally, the treatments notably increased soil organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium. The pot experiments demonstrated that microalgae treatments significantly enhanced wheat root lengths, seedling growth, biomass, chlorophyll content, as well as soluble sugars and proteins. Importantly, low-dose treatment with A. azotica surpassed high-dose effects on wheat growth, highlighting the cost-effectiveness and practicality of low-dose applications. This study offers a scientific foundation for further exploring the role of microalgae in remediating heavy metal pollution and promoting crop development.