Metals and Geochemical Indexes in Sediments of a Karstic Coastal Tropical Lagoon: Evaluating the Ecological Risk in Celestun, Yucatan, Mexico

Celestun is one of the most socio-environmentally important lagoons in Yucatan, Mexico, although it is vulnerable to contamination from in situ activities and to contaminants transported and released by the submarine groundwater discharges, mainly in the northern part of the lagoon. These contaminants, like metals, can accumulate in the sediments of the coastal lagoons and could eventually represent an ecological risk, thus, this research evaluate the enrichment factor, the geoaccumulation index and the ecological risk index to evaluate the environmental status of the lagoon. Sediments samples were collected during the main hydrological seasons, dry, rainy and Nortes, in selected sites. Results shown that metals distribution are related to (1) submarine groundwater discharges, (2) co-transport with fine materials in the rainy and Nortes season, and (3) in situ inputs from urban wastewater and agriculture. Cd, As and Sn were enriched in dry, rainy and Nortes season, going from minor to mildly sever enrichment, also, the geoaccumulation index indicated a minor to highly contaminated status, but the ecological risk was low. Metals are enriched and accumulating in the sediments, and although they represent a low ecological risk nowadays, this could change in the future as result of the economic development increase, that will release more wastewater and solid wastes that potentially could affect fisheries and human health.