In recent years, locally enhanced electric field treatment (LEEFT) has been considered as a novel and promising technology for efficient microorganism inactivation. Previous studies were primarily conducted on bacteria and viruses. Here, polydopamine-protected copper-oxide-nanowire-modified copper mesh (PDA-CuONW-Cu) electrodes were fabricated and utilized in a flow-through LEEFT device to treat two microalgae species, Chlorella vulgaris and Microcystis aeruginosa. The results showed that the LEEFT achieved efficient microalgae inactivation and growth control. The inhibition of F_v/F_m was 46.7% and 34.3% for C. vulgaris and M. aeruginosa, respectively, after five LEEFT cycles at a flow rate of 1.2 mL min⁻¹ and a 10 V alternating voltage with a frequency of 10⁴ Hz. Fluorescence staining and flow cytometry measurements verified the inactivation of microalgae cells, with dead cell ratios increasing to 61.3% and 56.5% for C. vulgaris and M. aeruginosa, respectively. Both species could still grow after removing the electric field, indicating that the LEEFT is a physical treatment process without residual anti-microbial effects. Nevertheless, with five LEEFT cycles, the 96 h-growth inhibition reached 60.1% and 66.2% for C. vulgaris and M. aeruginosa, respectively. The LEEFT can still be a promising control method for microalgae blooms when the LEEFT electrodes are durable enough for long-term circular treatment.

Harmful algal blooms are a global problem in water environments, and their explosive growth endangers the health of aquatic ecosystems. Magnetic nanomaterials for the harvesting of microalgae have received a lot of attention because of their high efficiency, low cost, and ease of operation. In this study, magnetic mesoporous silica nanomaterials were prepared using Fe₃O₄ as a carrier and harvesting on Chlorella sp. HQ. It was found that silica coated with magnetic Fe₃O₄ microspheres has good dispersion. The harvesting of Chlorella sp. HQ via magnetic mesoporous silica could be maintained over a wide pH range (4 to 12). After the removal of organic components from the surface of the material, the magnetic mesoporous silica obtained a better porous structure. The ethanol reflux method was more beneficial than the calcination method in maintaining the stable structure of the material, thus improving the harvesting efficiency of the material for the microalgae Chlorella sp. HQ by a maximum of 17.8% (65.9% to 83.7%). When the molar ratio of active agent cetyltrimethylammonium bromide (CTAB) and stabilizer polyvinylpyrrolidone (PVP) was 1: 0.092 at pH 4 and algal concentration of 0.5 g/L, the materials showed the maximum harvesting efficiency of Chlorella sp. HQ was 84.2%.

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant widely detected in aquatic ecosystems, but its subcellular targets and the mechanisms by which it disrupts light resource utilization in photosynthetic protozoa remain poorly understood at concentrations spanning environmentally typical to supra-environmental levels. Here, Euglena gracilis G.A. Klebs was exposed to PFOS at concentrations spanning environmentally typical (0.5 µg/L), hotspot-relevant (5 µg/L), and supra-environmental (50 µg/L) levels. Subcellular distribution, phototaxis, photosynthetic light reactions, and energy metabolism were investigated using isolated chloroplast assays, transcriptomics, and proteomics. TEM-EDS mapping revealed pronounced fluorine signal enrichment, attributable to PFOS, in the eyespot and chloroplasts. Eyespot fluorine enrichment was associated with impaired phototactic motility and an altered light perception threshold. PFOS did not acutely inhibit the maximum photochemical efficiency of photosystem II (Fv/Fm); instead, a transient upregulation of photosynthesis-related genes was observed, which weakened with prolonged exposure, whereas the photosynthetic electron transport rate (ETR) was significantly reduced. PFOS significantly reduced ATP levels and ETR, while Fv/Fm remained unchanged and non-photochemical quenching (NPQ) was elevated. Isolated chloroplast assays revealed that PFOS inhibits Mg²⁺-dependent ATP hydrolytic activity in the chloroplast-enriched fraction and impairs thylakoid electron transport, consistent with impaired chloroplast ATP synthase function, though the specific molecular target and mechanism remain to be conclusively demonstrated. Transcriptomic and proteomic analyses revealed compensatory upregulation of photosynthesis pathways but suppression of ATP synthesis and redox homeostasis. Collectively, our results suggest that PFOS impairs chloroplast ATP synthase function, accompanied by reduced ETR and elevated NPQ. Together with the eyespot-associated phototaxis impairment, these effects suggest that PFOS may dually disrupt light acquisition (behavioral) and light conversion (physiological) in E. gracilis. This dual impairment may compromise the ecological fitness of Euglena in PFOS-contaminated environments, especially under prolonged exposure. It should be noted that the subcellular fluorine mapping is qualitative, the phototaxis assay reflects population-level responses, and the ATP synthase impairment interpretation is indirect; the proposed mechanistic model remains a hypothesis requiring further direct experimental validation.