Mercury content of sarotherodon melanotheron and chrysischthys nigrodigitatus of Lake Nokoue and Porto Novo lagoon in Benin

Abstract

Ratification of Minamata Convention by Bénin requires identification of contaminated sites and preservation of health. In this context, the Ministry of Living Environment and Sustainable Development supported the study by making its mercury analyzer DMA80 available. The study aims to identify the level of mercury contamination in two highly valued fish species caught in one of the most productive water bodies where mercury is reported. So, three monthly sample collection campaigns were carried out from April to juin 2018 at nine (09) sites. The back flesh of sarotherodon melanotheron and chrysischthys nigrodigitatus of lake Nokoue and Porto Novo lagoon was analyzed by direct mercury analyzer (DMA 80). it Its operating principle is atomic absorption after thermal decomposition coupled with a gold sensor. The average mercury contents are 20.8 ± 15.5 μg / kg and 6.5 ± 3.8 wet μg / kg weight respectively for Chrysichthys nigrodigitatus and Sarotherodon melanotheron. The highest values obtained at the Porto-Novo bridge for both species remain well below the standard (0.5 mg / kg wet weight). With consumption habits of fish in Benin, the weekly exposure doses seem to be much lower than WHO recommendation. However, deepened studies are needed.

Keywords: Fish, mercury, spatial distribution, NoKoué Lake, Porto-Novo Lagoon.