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A two-fold integrated research study was conducted, firstly, to understand the effects of copper (Cu) and zinc (Zn) on the growth and oxidative stress in Nile tilapia, Oreochromis niloticus, secondly, to study the beneficial effects of the duckweed Lemna minor L. as a heavy metal remover in wastewater. Experiments were conducted in mesocosms with and without duckweed. Tilapia fingerlings were exposed to Cu (0.004 and 0.02 mg L&minus, 1) and Zn (0.5 and 1.5 mg L&minus, 1) and fish fed for four weeks. We evaluated the fish growth performance, the hepatic DNA structure using comet assay, the expression of antioxidative genes (superoxide dismutase, SOD, catalase, CAT, glutathione peroxidase, GPx and glutathione-S-transferase, GST) and GPx and GST enzymatic activity. The results showed that Zn exhibited more pronounced toxic effects than Cu. A low dose of Cu did not influence the growth whereas higher doses of Cu and Zn significantly reduced the growth rate of tilapia compared to the control, but the addition of duckweed prevented weight loss. Furthermore, in the presence of a high dose of Cu and Zn, DNA damage decreased, antioxidant gene expressions and enzymatic activities increased. In conclusion, the results suggest that duckweed and Nile tilapia can be suitable candidates in metal remediation wastewater assessment programs.

A two-fold integrated research study was conducted; firstly, to understand effects of copper (Cu) and zinc (Zn) on the growth and oxidative stress in Nile tilapia, Oreochromis niloticus; secondly, to study the beneficial effects of the duckweed Lemna minor L. as a heavy metal remover from wastewater. Experiments were conducted in mesocosms with and without duckweed. Tilapia fingerlings were exposed to Cu (0.004 and 0.02 mg/L) and Zn (0.5 and 1.5 mg/L) and fish fed for four weeks. We evaluated the fish growth performance, the hepatic DNA structure using comet assay, the expression of antioxidative genes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPx and glutathione-S-transferase, GST) and GPx and GST enzymatic activity. The results showed that Zn exhibited more pronounced toxic effects than Cu. Low dose of Cu did not influence the growth whereas higher doses of Cu and Zn significantly reduced the growth rate of tilapia compared to control, but addition of duckweed prevented weight loss. Further, in the presence of a high dose of Cu and Zn, DNA damage decreased, antioxidant gene expressions and enzymatic activities increased. In conclusion, results suggest that duckweed and Nile tilapia can be suitable candidates in metal remediation wastewater assessment programs.

Pollution of lakes and seas in Egypt become a severe problem as it produces a lot of wastes and toxic chemicals. The water pollution induces a lot of endocrine disruptions in aquatic organisms. Several endocrine organs are influencing by pollution such as testes, ovaries, pituitary, hypothalamus, thyroid, and adrenal organs. Propositions of upsetting endocrine chemicals (EDCs) can meddle with fish larval advancement affecting the delicate balance of the biological ecosystem. Endocrine disruption effects on reproductive cycles may affect reproductive behaviour and the development of secondary sexual characteristics. So the main objective of this research is to use marine algae, Dunaliella salina, extract in fish immunity enhancement against pollutants. Nile tilapia fish were exposed to Dioxin (as the main pollutant in the Egyptian environment) after feeding on algae extracts for one month. The results revealed that Dunaliella salina was able to protect the fish against pollution as it enhances the immune capability of Nile tilapia fish due to increase the levels of the antioxidant enzymes and decrease the protein oxidation. Additionally, Dunaliella salina extract was able to decrease the alteration in the expression of genes encoding endocrine hormones such as LH and FSH in the pituitary of Nile tilapia exposed to Dioxin in comparison to control fish. Moreover, the Dunaliella salina extract decreased significantly the DNA damage in brain tissues of Nile tilapia exposed to Dioxin compared with control fish. The results conclude that Dunaliella salina could be used as ameliorative compounds against toxicity of Dioxin.