Coastal lagoons are important but sensitive environments, being transitional zones between land and sea. The Khnifiss lagoon is the most important desert wetland in Morocco, but little data have been produced concerning heavy metal geochemistry and enrichments in the sediments. Therefore, 26 surface sediments (15 intertidal and 11 subtidal) and 2 sediment cores were collected in 2016 and analyzed for a selection of heavy metals. The data were processed to assess the degree of contamination and the corresponding potential ecological risk, using several accumulation/enrichment indices, and the singular and multi-metal risk indices. Mean concentrations in the bottom layers of the two cores, dating from a pre-industrial age according to geochronological analysis, were used as the local geochemical background. The resulting values were on the whole lower than those reported for other areas of the northeastern coast of Morocco. Multivariate statistics were also applied to better understand relationships among variables (metals and other geochemical parameters) and to reveal similarities among sample groups. The results showed that, although the lagoon is not yet affected by significant anthropogenic influences, small enrichments can be recognized, especially for Ni and Cd. The cause may be related to the proximity to the main national highway, the vehicles and machinery used in the saltworks located in the area, and the small harbors used principally for fishing. In addition, industrial emissions from the Atlantic coast of Morocco and adjacent countries can be reasonably attributed as additional contributors to the enrichments. In terms of potential ecological risk, Cd shows the greatest impact compared to the other metals investigated.

Surface sediments from Khnifiss lagoon (Morocco) were analyzed to evaluate the contamination degree of the area. Concentrations of V, Cr, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb were determined on samples taken during the summer and the autumn of 2016. On the whole, higher concentrations were found in the summer season. The results revealed the following average concentrations (mg/kg), reported in descending order: Zn (51.7 ± 31.3) > V (38.8 ± 24.7) > Cr (26.6 ± 17.8) > Ni (16.5 ± 5.47) > As (8.50 ± 2.00) > Cu (6.60 ± 3.81) > Pb (6.13 ± 3.46) > Co (3.57 ± 2.09) > Cd (0.16 ± 0.11) > Hg (0.006 ± 0.001). Organic matter showed a positive significant correlation with some trace metals (mainly V, Cr, Co, Zn, Cd, Pb). Three pollution indices were calculated: Enrichment Factor (EF), Index of Geo−accumulation (Igeo), and Pollution Load Index (PLI). Minimal enrichments (for Zn, As, and Cd) were detected at some sampling points. Overall indices showed that the Khnifiss sediments can be classified as not contaminated, and that the trace metals amounts found are ascribable to the geogenic origin. The results of this work can be used as a starting point for further evaluations of trace metals distribution in Moroccan lagoons.

The distribution, contamination status, and ecological risks of heavy metals in Tahaddart estuary were investigated. 24 surface sediment samples and two cores were collected and analyzed for major (Al and Fe), heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn), and grain size composition. The heavy metals assessment was carried out using different environmental indices. The results indicated that the spatial distribution patterns of Al, Fe, and Zn were mainly determined by the distribution of the finer grained fraction (<63 μm) in the sediment. In contrast, As, Cd, Cr, Cu, Ni, and Pb concentrations were controlled by anthropogenic activities (vehicular traffic from Highway Bridge and thermal power plant). The distribution of heavy metals in sediment cores showed an upward enrichment in heavy metals with high concentration found in the uppermost may related to the increasing in human activities. The pollution indexes confirmed that the Tahaddart estuary sediment was considerably to high contaminated by heavy metals near to different anthropogenic inputs. Similarly, the potential ecological risk index and the biological risk index present 21% probability of toxicity posing potential risk to the aquatic organisms. These results provide basic information that can be used to protect and improve the quality of this ecosystem.

Seagrass meadows exist in most shallow, sheltered, soft-bottomed marine coastlines and estuaries throughout the world and rank among the most productive systems in the ocean. Zostera noltei Hornemann is a small seagrass largely widespread in intertidal areas of Western Europe and North-West Africa, the Mediterranean Sea and in the Black Sea. In Morocco, intertidal Zostera noltei meadows were identified at six coastal ecosystems across c.a. 2500 km of its Atlantic coast (Tahaddart estuary, Moulay Bousselham, Sidi Moussa, Oualidia, Khnifiss lagoons and Dakhla Bay). The present work aimed at assessing the spatial and latitudinal variation of Z. noltei meadows by measuring the density of shoots, leaf biomass, root-rhizome biomass, number of leaf /shoot and the average length and width of leafs. Samples were conducted between December 2014 and January 2015, using a hand PVC corer (12.5 of diameter). When possible, a downstream and upstream comparison is performed in each site. Density of shoots fluctuated between 1972 and 9833 shoots m^-2. Leaves biomass varied between 32 and 259 gDW/m² and root-rhizome biomass oscillated between 21 and 314 gDW/m². Number of leaves per shoot fluctuated between 2.47 and 3.4 leaf per shoot, the leaf length between 4.9 and 30.8 cm and the leaf width 0.6 and 2 mm. These results showed, on the one hand, a clear spatial variation across a downstream-upstream gradient in each site and, on the other hand, a latitudinal pattern in the biomass and morphometry of the Z. noltei meadows across the Atlantic coast of Morocco. Significant differences were evidenced for all variables (ANOVA, p<0.05). The root-rhizome biomass and density of shoots are higher southward while the number of leaves per shoot, leaf biomass and the average length and width of the leaves are greater northward. These results are compared with literature data from the distribution range of Z. noltei. Further analysis regarding the genetics, the associated benthic invertebrates and the sediment contamination are being performed and will increase the knowledge on such ecosystems and help in understanding their interaction with environment conditions.