Unraveling the risks of nAl2O3 on harmful algal blooms: Insights from paralytic shellfish toxins production of Alexandrium tamarense

As one of the commonly used and cost-effective nanomaterials, nanosized aluminum oxide (nAl₂O₃) posses unique properties and chemical stability. However, its extensive use and resultant dissemination into aquatic ecosystems prompt concerns over the proliferation and repercussions of harmful algal blooms, particularly those caused by dinoflagellates producing toxins. This study investigated the sub-chronic effects of nAl₂O₃ on growth, physiological activities, and paralytic shellfish toxins (PSTs) production in Alexandrium tamarense. Results showed dose-dependent inhibition in growth (EC₅₀ = 20.6 mg L⁻¹), esterase activity, and photosynthetic efficiency (F_v/F_m) during the sub-chronic exposure (13-day). The internalization of nAl₂O₃ in microalgal cells and the significant decrease in the total cellular PSTs content were observed under high nAl₂O₃ concentrations (>40 mg L⁻¹). The study also demonstrated a clear decrease in the content of some derivatives of PSTs (GTX5, C1/2, and GTX2/3) with the increase in nAl₂O₃ concentrations, accompanied by the induction of an unknown derivative. Excessive ROS production, dissolved Al, and physical inhibition were suggested as potential mechanisms for _nAl₂O₃ toxicity and changes in PSTs toxin profile. Overall, this research enhances our understanding of the potentiated risks and threats on the possible concurrent events of toxic dinoflagellate, such as Alexandrium species and nanoparticles in aquatic environments.