Toxicity of TiO2 nanoparticles to the marine microalga Chaetoceros muelleri Lemmermann, 1898 under long-term exposure

Abstract

Titanium dioxide nanoparticles (TiO₂NPs) have been extensively used in industry, raising many concerns about their release into the aquatic environments. In marine ecosystems, microalgae are major primary producers; among them, Chaetoceros muelleri is an important microalga in the aquaculture industry as live feed. The impacts of TiO₂NPs on the growth, photosynthetic pigments, protein and lipid contents, and the interaction of TiO₂NPs with the cell wall of C. muelleri were investigated in the present study. Algal cells were exposed to concentrations of 5, 10, 50, 100, 200, and 400 mg/L TiO₂NPs for 10 days. There was a significant difference in the growth between the control and TiO₂NPs treatments on each day. The half-maximal inhibitory concentration (IC₅₀) of TiO₂NPs on algal cells was found to be 10.08 and 5.01 mg/L on the 3rd and 10th days, respectively. The contents of chlorophyll a and c reduced significantly in the TiO₂NPs-treated microalgae. TiO₂NPs also reduced the protein and lipid contents in the treated microalgae, up to 13.02% and 47.6% respectively, at the highest concentration. The interaction of TiO₂NPs with the C. muelleri cells was obvious based on Fourier transform infrared spectroscopy, microscopic images, EDS, and Mapping analyses. Toxic effects of the released TiO₂NPs can damage the stocks of C. muelleri as an important live feed in mariculture.

Keywords: Chaetoceros muelleri; Chlorophyll a; IC50; Nanomaterials; Toxicity.