Binary effect of titanium dioxide nanoparticles (nTio2) and phosphorus on microalgae (Chlorella 'Ellipsoides Gerneck, 1907).

The wide application of titanium dioxide nanoparticles and phosphorus in the manufacturing of many industrial products mainly used in agricultural sector has resulted in the release of considerable amounts of these compounds into freshwater aquatic ecosystem. These compounds may cause some unexpected effects to aquatic organisms. This study assessed the binary effects of Titanium nanoparticles (nTiO2) and Phosphorus on Chlorella ellipsoides. Toxicological assay test of the compounds nTiO2 (1.25 µM) alone and the combination of Titanium dioxide (1.25 µM) and Phosphorus (16, 32, 80, 160, 240 µM) was assessed, after 96 h exposures, for optical density (OD680), specific growth rate, chlorophyll levels and lipid peroxidation via Malondialdehyde (MDA) activity. Superoxide dismutase (SOD), peroxidase (POD) and glutathione-s-transferase (GST) activities were also measured. Two-way ANOVA showed a significant interaction (P < 0.05) between binary mixture. Co-exposure showed a decreased phosphorus bioconcentration in the microalgae with significant increase (P < 0.05) in chlorophyll a/b and total chlorophyll contents. A significant decrease (P < 0.05) in specific growth rate and optical density were recorded whereas, antioxidant enzymes (MDA, SOD, POD, GST) activities were significantly (P < 0.05) increased. These results showed that the addition of nTiO2 to Phosphorus affected the physiology of microalgae and should be of great concern for freshwater biodiversity.