Monitoring the Ecological and Geochemical Impacts of Coastal Development and Management on the Oualidia Lagoon

Oualidia lagoon, known as the oyster capital, is one of the most important coastal ecosystems along Morocco’s Atlantic coast. Over the past few decades, this ecosystem has faced numerous ecological challenges caused by both human activities and natural conditions, affecting its environmental quality. The present study aims to assess the impact of management projects implemented in the lagoon over the last eleven years on its health, especially in the sediment-trap area. In this context, a field mission was conducted in 2022, during which 15 surface samples were collected and analyzed using ICP-OES methods to determine metal concentrations. However, environmental indicators suggest that the ecological quality of the lagoon remains low, with significant and moderate contamination showing different trends, mainly for arsenic As (1–41.16 mg/kg); cobalt Co (2.01–7.2 mg/kg); molybdenum Mo (0–112.2 mg/kg); cadmium Cd (0.93–1.73 mg/kg); iron Fe (2433.36–19,721.55 mg/kg); and aluminum Al (640.7–11,600.57 mg/kg). The hotspots for these elements are mainly found at stations 13 and 15, which cover the upstream area of the lagoon near of the sediment trap. Comparing the results with those of previous studies conducted in the lagoon, there has been a decrease in sediment contamination since the sediment trap was created in 2011. The analysis suggests that different sources of these metals are entering the lagoon. This study provides updated data on metal concentrations in Oualidia lagoon sediments, one of the most diverse and biodiverse ecosystems in the Moroccan Atlantic. These results provide a scientific basis for targeted environmental management of the Oualidia lagoon, supporting priority monitoring and control of pollution sources. They also highlight the importance of developing awareness programs for residents, fishermen, farmers, food businesses, hotels, and guesthouse owners, alongside the continuation of management projects in the lagoon.