Due to the inevitable achievement of nanoparticles to aquatic ecosystems, the limitation of existing reports, and the inadequate understanding of their possible biological reactions with aquatic organisms, this study in the pioneering step was aimed to toxicity assessment of aqueous suspension of chemical magnetic nanoparticles (Fe₃O₄) in zooplanktonic species such as barnacle larvae Amphibalanus amphitrite (sea water index) and rotifer Brachionus rotundiformis (fresh water index). For this purpose, serial concentrations (0, 10, 50, 100, 200, 500 mg / l) of magnetite nanoparticles were prepared in 24 well plates with 5 replicates. After that, the zooplanktons (50 barnacle nauplii and 20 neonate rotifer to each well) were introduced to plates and the sensitivity of the samples were evaluated for the toxicity of nanoparticles at a time interval of 12-48 hours. The results of this study showed that the toxicity effects of chemical magnetite nanoparticles on barnacle nauplii larvae and neonate rotifer were increased with increasing time and concentration of magnetite nanoparticles. Differences between control and treatment groups were significant (P<0.05). However, after 48 hours of exposure, the mortality rate at the highest concentration (500 mg/l) in barnacles was 62% (LC₅₀= 466.5 mg/l) and in rotifer 34% (E₅₀>1000 mg/l). Regardless of species variation in barnacles and rotifers, according to the results, magnetite nanoparticles are in the group of non-toxic contaminants for these zooplanktonic organisms.

In this study, the toxicity of colloidal silver nanoparticles produced from three companies (US NANO, Pioneers, Nanonasb Pars) in the larvae of barnacles Amphibalanus amphitrite was evaluated using standard OECD. These crustaceans are important economically and ecologically. In this research, the LC₅₀ within 24 hours for nauplius stages II, III, IV, V and VI examined against toxicity of the three types of silver colloidal nanoparticles. The results suggested that the calculated LC₅₀ of silver nanoparticles from US NANO company for naupli II, III, IV, V and, VI, were 0.077, 0.046, 0.071, 0.006 and,0.009 mg/ml, respectively, and the LC₅₀ of silver nanoparticles from Pioneers company for naupli II, III, IV, V and VI were 0.122,0.5, 0.402, 0.013 and, 0.023 mg/ml, respectively. The evaluated LC₅₀ of silver nanoparticles from Nanonasb Pars for naupli, II, III, IV, V and VI were 0.259, 0.037, 0.018, 0.019 and, 0.017 mg/ml, respectively. This result indicated that silver nanoparticles of US NANO companys have been the most toxic on all larval barnacle stages and should be reviewed in correlation with the environment management products of silver nanoparticles.