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This study used the levels of pollutants and the histopathological analysis of the gonads and liver of Sarotherodon melanotheron sampled in Lake Nokoué and Lake Toho, both in Benin (West Africa) to assess the health status of the ecosystems. Sixty adults (30 males and 30 females) of this species were caught during the flooding seasons from both Lake Nokoué, and Lake Toho (as a reference). The physicochemical parameters of the water and the heavy metal contents (Pb, Cd, Hg) in water/sediment/fish of three sites (S1, S2, S3) in Lake Nokoué and two sites (S4, S5) in Lake Toho were analysed. Results confirm very strong organic status with organic pollution index ranging from 1.25 to 1.5. Pb, Cd, and Hg levels in the water/sediment/fish muscle tissue of Lake Nokoué were far exceeding international standards. The histopathology of gonads revealed testis-ova up to 40% in males and follicular atretic oocytes up to 33.33% in females, indicated oestrogenic effects from the pollutants with a delay of spermatogenesis and stimulation of oogenesis. The histopathology of the liver revealed the presence of regressive changes. The findings call for actions to protect the ecosystem from pollution and attention in terms of health of humans consuming fish products from Lake Nokoué. [ABSTRACT FROM AUTHOR]

This study investigated the acute toxicity in Clarias gariepinus to insecticides currently used in Benin cotton fields, including Thalis 112 EC (Emamectin benzoate 48 g L−1, Acetamiprid 64 g L−1), Vizir C 92 EC (Cypermethrin 72 g L−1, Abamectin 20 g L−1), Pyrinex Quick 212 EC (Deltamethrin 12 g L−1, Chlorpyrifos 200 g L−1) and Pyro FTE 472 EC (Cypermethrin 72 g L−1, Chlorpyrifos 400 g L−1) with emphasis on liver histopathological effects. A set of 180 juveniles of C. gariepinus (5.21 ± 3.22 g) was exposed for 96 h to increasing concentrations of each pesticide. The values of 96-hLC50 were 4.778, 0.002, 0.004, and 0.012 µL L−1 for Thalis, Vizir, Pyrinex, and Pyro, respectively, indicating that Vizir, Pyrinex, and Pyro were very highly toxic to C. gariepinus juveniles. During the experiments, the morphological and behavioral responses (discoloration, hyperactivity, lethargy, etc.) were observed in exposed fish, hypothesizing the neurotoxicity of these pesticides. Histopathological alterations observed in liver of contaminated fish were regressive changes, such as necrosis, vacuolation, bleeding, nuclear degeneration, hepatocytes degeneration, sinusoids dilatation, etc. Vizir induced the highest histological alteration indices while the lowest were induced by Thalis, confirming the highest toxicity of Vizir. These results indicate that acute concentrations of these insecticidal molecules have destructive effects on the liver of C. gariepinus. [ABSTRACT FROM AUTHOR]

Aquatic organisms are exposed to chemical pesticides including glyphosate (Sharp 480 SL) and atrazine (Atraforce), two phytocidal molecules used for agriculture purposes in Benin. In this study, we assessed the acute toxicity of these two herbicides with emphasis on their histopathological effects on the liver of catfish Clarias gariepinus. One hundred and eighty juveniles of C. gariepinus (mean length 7.26 ± 0.59 cm and mean weight 5.21 ± 3.22 g) were exposed over 96 h to increasing concentrations of each phytocide. The values of 96 h-LC50 were 6.175 × 103 and 3.165 ppm, respectively for Sharp 480 SL and Atraforce. This indicates that Sharp 480 SL was nontoxic, while Atraforce displayed a moderate toxicity to C. gariepinus juveniles. During the tests, the behavioral responses (hyperexcitation, lethargy, loss of balance, discoloration of skin, etc.) that usually precede death were observed in exposed fishes, confirming the neurotoxicity of these phytocides. Histological alterations observed in liver of contaminated fishes were regressive changes, such as necrosis, hepatocyte vacuolation, nuclear degeneration, hepatocytes degeneration, sinusoids dilatation, etc. These results indicate that exposure to these herbicides had destructive effects on the liver of C. gariepinus. [ABSTRACT FROM AUTHOR]

Few studies regarding the assessment of the growing season's trends and the associated agro-climatic risks are focused on agro-ecosystems around forest reserve although adaptive extensive agriculture poses severe threats due to climate variability and change. This study aims at analyzing the evolution of agro-climatic characteristics to identify the associated risks. It firstly consisted in analyzing the temperatures within the period from 1960 to 2016 in the forest reserve of "Trois Rivières." Secondly, the characteristics of the growing season and their distribution were analyzed. Statistic-based tests were further performed to identify major trends and breaks as well as the associated agro-climatic risks. Thus, the period from 2000 to 2016 generally presents wet conditions (increasing trends of Standardized Precipitation Index and rainy days) similar to the period of 1960 to 1975; which are separated by a relatively dry period (increasing trends of dry spells) from 1975 to 2000. Those facts reveals an apparent return to wet conditions after the 2000s which is coupled with the acceleration of warming resulting in the increase of minimum temperatures by 1.5 °C and the maximum by 1 °C. We also noticed a great variability of the dry spells within the growing season which has accentuated especially the risk of sowing failure (false start) by 56 to 74% and the yields failure risks by 52%. Our findings showed the degree to which farmers are affected by the realities of climate variability and change in "Trois Rivières" forest agro-ecosystems. That led farmers, mostly poor, to resort to extensive agriculture which unfortunately is the main cause of deforestation. [ABSTRACT FROM AUTHOR]

An in-situ study combined with an integrated biomarker response was used to evaluate the impact of agricultural effluents in the physiological responses of Nile tilapia reared in cages and enclosures of water reservoirs in North Benin. Fish were distributed in fish farming systems at two sites: Songhai located outside the cotton basin and Batran located in the most productive commune. They were sampled for blood and organs before (BST), during (DST) and after (AST) pesticide treatment. Pesticide residues were analysed in water, sediments and fish muscles. Several biomarkers were investigated related to the immune (peroxidase, lysozyme and complement activities, superoxide anion production) and reproductive (sex steroids and vitellogenin levels) responses as well as neurotoxicity (cholinesterase activity) and tissue alterations. Biomarkers were assessed and analysed via the integrated biomarker response (IBR). The results showed that Batran water reservoir was a more harmful ecosystem for fish than Songhai one, especially by depressing some immune and reproductive functions in relation to a higher-level of pesticide contamination. They also demonstrated that the contact of fish to sediments in enclosures aggravated the pesticide burden on fish. Therefore, using males as bioindicators would improve the sensitivity of the used biomarkers since males seemed more affected than females especially due to pesticide estrogenic induction impacting their reproductive system. [Display omitted] • Impact of pesticide residues was investigated in two sites and types of infrastructure in cotton field areas in north Benin. • Several biomarkers were assessed and analysed via the integrated biomarker response. • Batran water reservoir constituted a harmful ecosystem for fish. • Access to sediment aggravates the pesticide burden on fish. • Using males as bioindicators would improve the sensitivity of the integrated biomarker response. [ABSTRACT FROM AUTHOR]