Abstract
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−1) and Zn (0.5 and 1.5 mg L−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.
Highlights
Among the major health concerns worldwide is the massive release of toxic compounds into the natural environment including soil and water [1,2]
The applied dosesliver of Cucells and of ZnNile weretilapia chosenOreochromis based on theniloticus estimated levels in concentrations
The results show that a high dose of Cu (0.02 mg L ) and Zn measurements wereactivity performed toofexamine hepatic
Summary
Among the major health concerns worldwide is the massive release of toxic compounds into the natural environment including soil and water [1,2] Many of these compounds are defined as metals and are dangerous even at minimal concentrations and which may be cytotoxic, carcinogenic and mutagenic in nature [3,4]. They occur in the environment from natural and anthropogenic sources [5,6] Dietary contamination by these chemical elements gives rise to numerous adverse effects on human and animal physiology [1,2,7,8]. These compounds may seriously affect cellular processes [7]. An overexpression of free radical production or a downregulation of radicals-scavenging activity alters cellular functions through the direct modification of biomolecules and by the alteration of signaling pathways [7]
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