Assessing contamination risk zones with water age modeling in Terminos Lagoon, Southeastern Coastal Mexico

Understanding the time scales of water transport in semi-closed ecosystems is essential for assessing the behavior of pollutants in coastal lagoon environments. Terminos Lagoon, Mexico's largest lagoon-estuarine system, is under significant environmental stress. We used a water age tracer combined with a high-resolution 3D hydrodynamic model to evaluate the lagoon's zones of accumulation and exchange. Our findings revealed a year-round counterclockwise circulation in the lagoon, which allows seawater to enter through Puerto Real and exit via Carmen Inlet. The inner littoral of Carmen Island features relatively young water currents, with an average age of 60 days. In contrast, the lagoon's center contains older water parcels, averaging 130 days. The southern and southeastern littoral regions hold older water areas, with the Candelaria Estuary showing the oldest waters, reaching up to 250 days. This emphasizes the Candelaria Estuary as a crucial area at risk of environmental impacts due to contaminant accumulation in the lagoon. As the primary inflow of seawater occurs through the Puerto Real inlet, it is vital to establish management strategies to minimize potential pollutant releases in the area.