Abstract
The protection of aquatic ecosystems is of great importance to maintain the biological balance necessary to secure healthy foods therein imbedded. Toho Lake, located to the south east of Benin, is threatened by pollution emanating from anthropogenic activities with the use of chemical fertilizers, effluent of domestic waste, particularly human and animal excrement with neighbourhood effluents. This study aimed at assessing some heavy metals in fresh fish (Oreochromis aureus) of Toho Lake in order to secure healthy food for the population and protect the ecosystem. Samples of water and fishes were collected and analyzed by HACH DR 3900 after treatment. Results revealed a mean oxygenation of water (4.95 mgo2/l), Biochemical Oxygen Demand (21.5 mgo2/l), Chemical oxygen Demand (149, 39 mg/l) with the nitrogen in Nitrate (NO3: 0.18 mg/l), ammonium nitrate (N-N: 0.47 mg/l), and phosphorous (2.06 mg/l) to be very high. The highest contents of heavy metals obtained in the fresh fish were cadmium (32.25 mg/kg), copper (115 mg/kg), lead (8.25 mg/kg), and zinc (90.75 mg/kg) and revealed that the fishes of Toho lake were polluted. The finding allowed us to conclude that the pollution of the lake and the fish carnage are due to anthropogenic pollution through chemicals spilling. Some protection methods of the lake and ecosystem are proposed in order to keep the fish safe and protect the well-being of the population.
Highlights
Pollution of surface and ground water is a major problem due to rapid urbanization and industrialization
This study aimed at assessing some heavy metals in fresh fish (Oreochromis aureus) of Toho Lake in order to secure healthy food for the population and protect the ecosystem
The finding allowed us to conclude that the pollution of the lake and the fish carnage are due to anthropogenic pollution through chemicals spilling
Summary
Pollution of surface and ground water is a major problem due to rapid urbanization and industrialization. The pollution affects dangerously available water resources and caused many issues to the drinking water in the world. These past years, many African countries saved a demographic growth which leads to the acceleration of the urbanization and the use of large surface by agricultural and industrial activities. All these side effects of development are not well managed, the solid and liquid garbage, effect of various pollutants thrown in the watercourses, and disturbing the different aquatic environmental components and reduce the fishing productivity. The presence of the chemical products can cause the death of animals and plants and can be the source of animal or plant extinction, leading to the dysfunction of the trophic chain (Gold et al, 2002)
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