The legacy of arsenic and mercury in the Ramsar Ayapel wetland complex (Córdoba, Colombia): An approach to the Magdalena-Cauca macro-basin

Abstract

Located in the northern extreme of South America, Colombia is one of the most mercury contaminated countries in the world, a situation that threatens its natural wealth and highly endemic neotropical biodiversity and adds to its multiple environmental and social conflicts. Internationally designated as a Ramsar site, the Ayapel wetland complex registers the catching of 23 % of the fish production of the Magdalena-Cauca macro-basin, while at the same time is under intense alluvial mining pressure. Exposure to two endocrine disruptors [mercury (Hg) and arsenic (As)] was traced in fish for human consumption, water and sediments collected in the central marshes of Ayapel, Escobillas and Paticos. Previously unreported concentrations of arsenic were found in sediments and water. This is quite a relevant finding, since it is a carcinogen and because local rice crops are supplied by the water of the marsh system, which may increase toxicological risk for the people of the region. In addition, 96 % of the fish registered statistically significant contents of both Hg and As. The fish blanquillo (Sorubim cuspicaudus) was found to contain the highest levels of both pollutants, while the bocachico (Prochilodus magdalenae) registered the highest level of Hg in the last 15 years for the studied area. Framed in mercury variation in the macro-basin´s ichthyofauna (1993-2020), a warning is issued about unmonitored impacts on food webs and the urgency of intersectoral actions to protect biodiversity and human health.