Tolerance and bioaccumulation mechanisms of the microalgae Scenedesmus obliquus to beryllium ions: Insights from physiological and transcriptomic responses

Beryllium (Be) is a widely utilized industrial metal with favorable physicochemical properties but poses severe chronic toxicity to aquatic organisms and humans, mandating safe and efficient removal from aqueous solutions. Current algal biosorption research remains limited for Be 2+ separation and underlying molecular mechanisms. In this study, the green microalgae Scenedesmus obliquus was exposed to varying concentrations of BeSO 4 (0.01, 0.1, 1.0, 10.0, and 20.0 mg/L), and its growth, photosynthesis, oxidative stress response, Be 2+ removal performance, and transcriptomic responses were investigated. Short-term exposure to BeSO 4 had negligible effects on microalgal cell growth, chlorophyll a content and antioxidant system, whereas high dose (20.0 mg/L) or prolonged exposure (4 days) significantly inhibited these processes. The total bioaccumulation amount of beryllium increased continuously with elevating BeSO 4 concentrations, ranging from 0.002 mg to 3.53 mg. Although the beryllium removal efficiency was relatively lower under 1 mg/L BeSO 4 treatment (40.02%), it exhibited a steady increase with rising BeSO 4 concentration and ultimately reached 88.14% at 20.0 mg/L BeSO 4 on day 1. Transcriptomic analysis revealed that most genes associated with photosynthesis (44 transcripts), antioxidant system (33), stress response (60), nitrogen metabolism (46), endocytosis (38), and ion binding and transport (86) were upregulated, contributing to the high tolerance and total bioaccumulation of S. obliquus to beryllium ions. These findings revealed physiological and molecular mechanisms of beryllium tolerance and bioaccumulation in S. obliquus , providing a scientific foundation for the treatment of beryllium-containing wastewater and aquatic bioremediation.