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Copper and nickel are of essential trace elements, which could be entered into aquatic ecosystems through various ways due to their broad applications in agriculture and industrial activities. The acute concentrations of these metals results in aquatic animal death and therefore, removing the planktonic community of aquatic environments. This, in turn, accounts as a serious threat to other living organism through eliminating the first trophic level of a food chain. In this study, we investigated the copper (CuSO₄.5H₂O) and Nickel (NiSO₄.6H₂O) toxicity effects on Daphnia magna neonates as a model in ecotoxicology in 2016. To address that, 60 neonates were individually exposed to 6 different concentrations of copper, including zero or control, 0.4, 0.6, 0.9, 1.35 and 2.25 µg/l, and 6 different concentrations of nickel, including zero or control, 18, 32, 58.32, 104.98 and 188.96 µg/l for 48h. According to the OECD protocol no. 202; immobilization was determined following 6, 24 and 48 h time intervals. The obtained results indicate that EC₅₀-24 and -48 h for copper were 0.931 and 0.667 µg/l respectively. The EC₅₀-24 and -48h for nickel were obtained 163.24 and 50.06 µg/l respectively. In conclusion, our findings showed that copper is more toxic than nickel in the case of D. magna neonates. Therefore, due to widespread use of copper as an antiseptic on fish farms, more attentions should be paid into the consumed concentration of this metal. This will likely prevent removal of zooplankton community in fish ponds as well as aquatic ecosystems.

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Aquatic plants have a high and different capacity to absorb heavy metals. Therefore, their use is recommended as an inexpensive and environmentally friendly method to remove metals from contaminated environments. In this study, accumulation, bio-concentration and transfer factors of two heavy metals nickel and cadmium by three plant species Scirpus tabernaemontani, Phragmites australis and Typha latifolia by applying three levels (nickel with levels of 20, 50 and 150 mg/kg and cadmium levels of 10, 35 and 85 mg/kg) cultured in pot culture medium with a sandy bed for 60 days in winter of 2017 were studied. After preparing the substrate, adding nutrient chemicals and concentrating the substrate to the studied metals, each culture medium was randomly assigned to one treatment in three replications. The results showed that the effect of different levels of concentration of both metals and type of aquatic plant on accumulation in plant organs was significant. Also, the accumulation of the two studied metals in the underground organs was far more than the same values in the aerial organs. Maximum amount of nickel accumulation was observed in underground and aerial organs related to Typha latifolia with values of 71.6 and 35.8 mg/kg and 34.6 and 12.5 mg/kg in dry matter for cadmium. The highest transfer factor about nickel and cadmium were recorded for Typha latifolia with values of 0.44 and 0.34. In terms of bio-concentration factor, Phragmites australis and Typha latifolia with values of 0.68-0.78 and 0.71-0.84 for cadmium, and 0.48-0.70 and 0.58-0.70 for nickel are in ranges are considerable. Due to the fact that the present experiment was conducted in the warm season in Khuzestan, due to the high air temperature, high evapotranspiration of aquatic plants can be a good reason to absorb more heavy metals.