Effects of the watershed on the seasonal variation of the surface water quality of a post-restoration coastal wetland: The case of the Nador lagoon (Mediterranean sea, Morocco)

Abstract

The Nador lagoon is a coastal wetland which is subject to both the watershed pressures and land runoffs coming from domestic, agricultural, industrial and mining pollution. In 2017, 19 stations encompassing the entire lagoon and pollution sources, including 13 at the lagoon level and 6 at the watershed level, were sampled during wet and dry seasons. Descriptive and multivariate statistical analyses were used to assess its environmental status through physio-chemical, nutrients and trace metals parameters. The results show that seasonal variations significantly affected the concentrations of Fe, Cu, Cr, and Cd in the lagoon. The highest mean concentrations were recorded for Mn, Zn, Cr and Pb during the wet season and for Fe, Cu, Ni and Cd during the dry season. The average concentrations of Pb, Cd, Cr, Zn and Mn in the lagoon were lower than the USEPA 2016 standards on saltwater aquatic life preservation while the average concentrations of Ni and Cu are higher. In order to preserve this wetland, the implementation of an environmental management plan is required focusing on the rehabilitation of the iron mining area, the extension of the sewerage network, the control of agricultural effluents and the upgrading of industrial pollution controls.