Titanium dioxide nanoparticles (nTiO2) have raised environmental concerns and display potential hazards to aquatic organisms and even humans. However, only a few reports tested the toxicity of nTiO2 to rotifers. In the present study, acute and chronic toxicity of nTiO2 to the freshwater rotifer Brachionus calyciflorus was investigated at different temperatures. At 25°C, the 24 and 48‐hr LC50 was 117.14 and 60.11 mg/L, respectively. At 15°C, 20°C, 25°C, and 30°C, exposure to nTiO2 significantly decreased life expectancy at birth, net reproductive rate, generation time, average lifespan, and/or intrinsic rate of population increase of B. calyciflorus (p < .05). High temperature enhanced the toxicity of nTiO2 to rotifers. The swimming linear speed of rotifers significantly increased (p < .05) in treatments with 200 µg/L nTiO2, compared with the control. In addition, treatments with 8 µg/L to 5 mg/L nTiO2 significantly increased superoxide dismutase activity (p < .05). Glutathione content and catalase activity increased significantly after exposure to 8 µg/L nTiO2 but decreased significantly in treatments with nTiO2 concentrations ranging from 40 µg/L to 5 mg/L (p < .05). There were no significant changes in malondialdehyde contents among nTiO2 treatments and control. Overall, the present study indicated that nTiO2 revealed high toxicity to rotifers, displaying high environmental risks to aquatic ecosystems.

Hg 2+ and Cu 2+ are two typical contaminants. Environmental pollution of Hg 2+ and Cu 2+ have been observed globally. Hg 2+ is high toxicity to human beings and environments due to its bioaccumulation and biomagnification within trophic levels [1]. Hg 2+ could be transformed to methylmercury, which is even more toxic [2]. Hg 2+ and derivates can cause severe disorders to organisms, including neurological, immunological, cardiac, motor, reproductive and genetic toxicity, and also is associated with Alzeihemer's, Parkinson's, autism, lupus, and amyotrophic lateral sclerosis [3,4]. Recent molecular studies have revealed that Hg 2+ treatment decreased many critical processes, including ferric iron binding, antioxidant activity, cellular homeostasis, and glutathione metabolism in copepod

Microalgae are biological indicators of heavy metal pollution. Cadmium (Cd) and lead (Pb) are extremely toxic metals to aquatic organisms. In the present study, single and combined toxicity of Cd 2+ and Pb 2+ to Scenedesmus acutus and Schroederia sp. collected from the famous Xin'an River (Huangshan City) were evaluated. Treatments with 0.5-2.0 mg/L Cd 2+ significantly reduced S. acutus population growth, and treatment with 2.0 mg/L Cd 2+ significantly decreased Schroederia sp. population growth rate, suggesting a higher tolerance of Schroederia sp. than S. acutus to Cd 2+ pollution. In addition, Cd 2+ treatments significantly decreased chlorophyll a, carotene contents, and photosynthetic fluorescent parameters rETR max and I k , demonstrating that the harms on photosynthesis might be the underlying mechanism of Cd 2+ toxicity to algae. Treatments with 5.0-15.0 mg/L Pb 2+ did not significantly affected population growth and photosynthetic pigment content. However, combined exposure to Cd 2+ and Pb 2+ revealed antagonistic effects on both species. Overall, these results provide basic information to the ecological risk assessments of heavy metal pollution in the Xin'an River Basin.

Cd 2+ is a serious environmental pollutant. Previous studies have investigated the effects of Cd 2+ on animals, plants and algae. However, the tested concentrations were generally higher than the actual environment level. The present study determined the effects of low concentrations of Cd 2+ (0.05 to 0.20 mg/L) on the chlorophyll fluorescent parameters of six local algae species in order to investigate the early toxicity of Cd 2+. The results showed that treatments with up to 0.20 mg/L Cd 2+ did not significantly affect population growth rate of S. quadricauda, C. pyrenoidosa, S. obliquus, N. palea, S. minutum and S. acutus. Treatments with 0.05-0.20 mg/L Cd 2+ significantly increased F v /F m in N. palea and S. minutum and decreased F v /F m in S. obliquus and S. acutus, but did not significantly affect F v /F m in C. pyrenoidosa. When exposed to Cd 2+ , rETR max was reduced in S. obliquus, C. pyrenoidosa, S. acutus and S. quadricauda, but was elevated in N. palea and S. minutum. Overall, trace Cd 2+ still revealed early toxicity to green algae. N. palea, S. minutum and C. pyrenoidosa were more tolerant to Cd 2+ than S. obliquus, S. acutus and S. quadricauda.