Phytoremediation of wastewater toxicity using water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes).

This paper elucidates the phytoremediation potential of water hyacinth and water lettuce on the reduction of wastewater toxicity. Acute toxicity tests were performed in an aquarium with a population of Sarotherodon melanotheron, contaminated by different concentrations of wastewaters before and after phytoremediation with Eichhornia crassipes and Pistia stratiotes. Lethal concentrations (LC50) of the fish's population obtained during 24 hours of exposures were determined. COD, BOD, ammonium, TKN and PO4(3-) concentrations in wastewaters were of 1850.29, 973.33, 38.34, 61.49 and 39.23 mg L(-1), respectively, for each plant. Phytoremediation reduced 58.87% of ammonium content, 50.04% of PO4(3-), 82.45% of COD and 84.91% of BOD. After 15 days of the experiment, metal contents in treated wastewaters decreased from 6.65 to 97.56% for water hyacinth and 3.51 to 93.51% for water lettuce tanks. Toxicity tests showed that the mortality of fish exposed increased with increase in concentration of pollutants in wastewaters and the time of exposure. Therefore, the highest value of LC50 was recorded for fish subjected to 3 hours of exposure (16.37%). The lowest rate was obtained after an exposure of 20 to 24 hours (5.85%). After phytoremediation, the effluents purified by Eichhornia crassipes can maintain the fish life beyond 24 hours of exposure.

Cadmium accumulation in tissues of Sarotherodon melanotheron (Rüppel, 1852) from the Aby Lagoon system in Côte d'Ivoire.

This study assessed the concentrations of cadmium in the gills, livers and muscles of a commercially important tilapia fish (Sarotherodon melanotheron) from Aby Lagoon in Adiaké, Côte d'Ivoire, between January and December, 2010. The organisms were grouped into two composite samples (juvenile and adult) of five individuals. Levels of cadmium were determined in tissues using Perkin-Elmer (AAnalyst 200) Atomic Absorption Spectrophotometry (AAS) after a digestion method. Fish muscle appeared to have a significantly higher tendency to accumulate cadmium (1.19-5.18 µg/g dw) while gills and livers had minimum concentrations (0.07-1.32 and 0.12-1.25 µg/g dw). This study has revealed that the concentrations of Cd in Sarotherodon melanotheron muscle tissue were above the maximum acceptable concentrations for human consumption, thus precautions need to be taken in order to prevent future contamination.

Histological analysis of the impact of lagoon pollution on Chrysichthys nigrodigitatus from Cote d'Ivoire.

Immunohistological and histopathological methods were used to highlight the importance of cell damages and some biomarkers for health risk assessment. A comparative study between 3 sites of the lagoons showed that the most polluted areas (Adiake and Ebrah), influenced by human activities, presented more damaged cells and stained cells in gills and livers of Chrysichthys nigrodigitatus than the less polluted area (Layo): gill cell hyperplasia and liver cells vacuolation were more evident in fish from Adiake than in fish from Ebrah and Layo. The percentage of proliferating cell nuclear antigen (PCNA)-positive cells in gill were 45.8 % ± 23.7 % for Adiake, 18.2 % ± 4.6 % for Ebrah and 11.4 % ± 6.51 % for Layo; The percentage of PCNA-positive in liver cells were 3.8 % ± 3.6 % for Adiake, 4.9 % ± 4.7 % for Ebrah and 2.6 % ± 2.5 % for Layo. Gills were more affected than livers. The Adiake site was the most contaminated area of the lagoon complex of Cote d'Ivoire.

First ecotoxicological assessment assay in a hydroelectric reservoir: the Lake Taabo (Côte d'Ivoire).

Organochlorine pesticides (OCPs) contamination was assessed in marketable species, two fishes (tilapia and catfish) and a prawn from the Lake Taabo (Côte d'Ivoire). Lindane and endosulfan were the main contaminants, suggesting their current use. DDT, endrin, heptachlor plus traces of chlordane, aldrin and fipronil were also detected. In fishes and in prawns, enzymatic biomarkers exhibited significant correlations with OCPs levels, showing the feasibility of a biomonitoring. The transfer of OCPs along the aquatic food web and their immunosuppressive effects in human are discussed. This preliminary study highlights that the pesticide contamination was concomitant with the increase in infectious diseases in the bordering population of this African lake.