Seasonality of Hg dynamics in the Ebrié Lagoon (Côte d'Ivoire) ecosystem: influence of biogeochemical factors.

This study addresses the different biogeochemical parameters that control the dynamics of Hg, which is a less-studied metal in the Ebrié Lagoon. During two hydrological seasons, the dry season and the rainy season, we regularly sampled and analysed various compartments (e.g. sediments and fishes (Tilapia sp.)) of the lagoon. Thus, the physicochemical parameters were measured in situ (e.g. temperature, pH, salinity, redox potential and dissolved oxygen, total dissolved organic carbon, nitrates and sulphates), and the microbiological parameters (e.g. cultivable cells, total enzymatic activity and catabolic activity) were measured to establish the seasonal variations in the links between Hg and biogeochemical parameters through multivariate statistical analyses. The bioavailability of Hg from an unpolluted site was studied by comparing the ratios of fish and sediment. The results indicated that the seasons influenced the different biogeochemical factors, although for some factors, the variations were not significant. This influence was more pronounced in the dry season than in the rainy season. The impact of microbial activities and organic matter on Hg dynamics was observed in all seasons. However, other factors, such as pH, temperature, salinity, Eh and sulphates, influenced the dynamics of Hg only in the dry season.

Vulnerability and adaptation to climate change in the Comoe River Basin (West Africa).

Climate change is impacting water users in many sectors: water supply, farming, industry, hydropower, fishing, housing, navigation and health. Existing situations, like population growth, movement of populations from rural to urban areas, poverty and pollution can aggravate the impacts of climate change. The aim of the study is to evaluate the vulnerability of different water user groups to climate change and define communities' adaptation strategies in the Comoe River Basin. Information was collected on communities' concerns and perception on changes in climate and potential adaptation measures and strategies. Results show that 95 % of the sample in the study communities had heard of it and are aware that climate change is occurring. They have been experiencing changes in economic activity and cropping pattern, reduced water level in rivers, crop failure, delay in cropping season, new pests and diseases, food insecurity, drop in income and decline in crop yield. Results also show that communities employ various adaptation strategies including crops diversification, substitution and calendar redefinition, agroforestry, borrowing from friends and money lenders and increasing fertilizer application.