P. tricornutum and A. franciscana were used to investigate nTiO2 and TiCl4 toxicity. Brine shrimps exposure included standard and alternative scenarios. Toxicity for microalgae was: TiCl4 > nTiO2. Toxicity for brine shrimps was: TiCl4 < nTiO2. Dark conditions minimized adverse effects of nTiO2 conversely to starvation.