LAUSR

In this study, the impact of alpha‐iron oxide (α‐Fe2O3, 20‐40 nm) and gamma iron oxide (γ‐Fe2O3, 20‐40 nm) nanoparticles (NPs) on phytoplankton species Selenastrum capricornutum and Nannochloropsis oculata was investigated Characterizations of the NPs were systematically carried out by TEM, dynamic light scattering, zeta potential, X‐ray diffraction, SEM, and Fourier transformation infrared spectroscopy. Acute toxicity was tested between 0.2 and 50 mg/L for each NP for a period of 72 hours exposure. γ‐Fe2O3 NP inhibited development of N oculata at the rate of 54% in 0.2 mg/L group with a high mortality rate of up to 82%. α‐Fe2O3 NPs were less toxic that induced 97% mortality on N oculata at 10 mg/L suspensions. In contrast, α‐Fe2O3 NP inhibited growth of S capricornutum strongly (73%) in 0.2 mg/L group. γ‐Fe2O3 NPs showed similar growth inhibition (72%) on S capricornutum in 10 mg/L suspensions. Despite the differential effects, the results indicated acute toxicity of α‐Fe2O3 and γ‐Fe2O3 NPs on N oculata and S capricornutum.