Socio-environmental evaluation of a lagoon ecosystem: the case of Moulay Bouselham lagoon, Atlantic coast of Morocco.

Lagoon ecosystems represent the most vulnerable ecosystems, often subject to multiple anthropogenic pressures, including numerous disturbances in terms of hydro-sedimentary dynamics. The lagoon of Moualy Bouselham, also known as "Merja Zerga", located on the Atlantic coast of Morocco. This lagoon was included in the RAMSAR list of wetlands on June 20, 1980. It hosts several important human activities including fishing. Nevertheless, the growth of urbanization and the development of economic activities, including the overexploitation of natural resources (fishing, agriculture), continuously lead to serious changes in the physical, chemical and biological state of the lagoon. These changes include, mainly, water and sediment pollution by heavy metals, closure of the main entrance inlet, loss of biodiversity, and, consequently, a decrease in the availability of ecosystem services (ES). Today, the lagoon suffers from a growing containment problem due to the significant increase in the amount of sediment, especially in the entrance zone, which leads to the accumulation of sand and the creation of sandy areas called "sandpits". This situation presents a risk of closure of the inlet, leading to further environmental degradation and economic problems. Aware of the magnitude of this problem, the decision makers proposed a study to reduce sand deposits by suggesting the most practical options in terms of hydrodynamic improvements inside the lagoon. In this sense, this study focuses on the relationships between socioeconomic factors and their impacts on the lagoon environment. To this end, a DPSIR approach is used, describing the causal links between "driving forces" (economic sectors, human activities), "pressures" (emissions, wastes), "states" (physical, chemical, and biological), and "impacts" on ecosystems, human health, and functions, ultimately leading to policy "responses" (prioritization, target setting, indicators). Likewise, some management proposals were discussed in this study, taking into account the current state of the lagoon as well as the ecological sustainability and well-being of the local population. On the other hand, this work focuses on hydro-sedimentary modeling using the numerical model Mike 21 to assess the hydrodynamic balance of Moulay Bouselham lagoon in order to participate in the management of this ecosystem to maintain its sustainability and protect natural resources.