Pollution assessment around a big city in West Africa reveals high concentrations of microplastics and microbiologic contamination
Résumé
Marine pollution around West African big cities is of major concerns. Nevertheless, few attempts have been performed so far particularly on microplastic assessment. We had led first survey targeting microplastic in West African coastal waters (2016); and evaluated on the same sites microbiological contamination as well as marine sediment toxicity and mercury content. Thus, neuston marine water samples were collected over Dakar a highly populated West African city. The average abundance was around 258 954 microplastic particles per km2 and 37 442 for macroplastics. One station, downstream from the major wastewater plant, contained high abundance of microplastic particles of over 945 000 and 190 000 macroplastics. The offshore station had a lower abundance of microplastics and macroplastics. It was observed that the stations found with highest level of microbiological pollution were related to highest microplastics abundance and the presence of major effluents, suggesting wastewaters inputs and microbiological pollution favoured by microplastics and macroplastics as vector. No correlation was observed between microplastics and/or macroplastics and sediment toxicity neither mercury level, which appeared low in all studied sites. However, high level of ecotoxicity were often found near effluents. Such results are a first step within the framework of encouraging awareness and actions in West Africa.