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 mgo 2 /l), Biochemical Oxygen Demand (21.5 mgo 2 /l), Chemical oxygen Demand (149, 39 mg/l) with the nitrogen in Nitrate (NO 3 : 0.18 mg/l), ammonium nitrate (N-NH + 4 : 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.

The protection of aquatics ecosystems leads to the biological equilibrium which secures the safe foods from the aquatics products. Toho Lake located to the southeastern of Benin is threatened by human pollution due to the chemical fertilizers, waste housekeeper, and both human and animal excrement result agglomeration. The aim of the present study is to Toho lake protection against chemical and bacteriological pollution of these wet ecosystems. Samples of water and sediment were collected and analyzed by HACH DR 3900 after undergone treatment The different analysis results revealed mean oxygenation of water (4,95mgo2/l), the Biochemical Oxygen Demand (21.5 mgo2/l), the Chemical Oxygen Demand (149, 39 mg/l) with the azote in Nitrate (NO3:0,18mg/l), ammoniacal azote (N-NH4 + :0,47mg/l) phosphorous (2,06mg/l) are very high. The lake is also polluted by fecal matters. The high contents of heavy metals in the sediment show that the sediments of the lake are polluted by the zinc (340mg/kg), the cadmium (7mg/kg), the lead (60,75mg/kg), and the copper (8,25mg/kg).

The waste management is a major environmental challenge in all the countries. In the Republic of Benin, in absence of controlled landfill, the wetlands are filling in by solid household waste to set up housing environments. This study aimed at identifying the various forms of wetlands water pollutions originated by this practice. Physico-chemical parameters of sampling water were determined by using Ionic chromatography and spectrometry of atomic absorption. The microorganisms indicating fecal peril were identified by the conventional techniques of microbiology. Water quality of a witness well was also used to assess the general water quality of the backfilled wetland. The results revealed the water samples collected from backefilled wetlands were mineralized (898.32 ± 6.13 µs/cm), rich in chlorinate (237.80 ± 4.23 mg/L) and nitrates ions (224.10 ± 3.42 mg/L). They are more colored (399.23 ± 3.01 Pt/Co) and more turbid (62.5 ± 2.48 NTU) than those of the unfilled wetlands. The results of microbiological analysis shown the presence of the cysts of Giardia lamblia (590/100 L) and cysts of Entamoeba histolytica (13/100 L) in all water, except those of witness well. The frequency of water contamination by bacteria indicating general degradation is 86.4%. The embankment of the wetlands by the solid household waste leads to the water pollution.