Heavy metals in coastal ecosystems caused by the increased expansion of urbanization, industrialization, and agricultural practices have become a significant environmental risk to human well-being. This study evaluates and compares 17 sediment quality indices to examine the possible ecological and human health risks associated with heavy metal concentrations in the sediments of the Nador lagoon in Morocco. The concentration order of the HMs and sulfurs evaluated was S > Sr > Ba > V > Zr > Zn > Cr > Rb > La > Cu > Pb > Ni > Ce > Nd > Co > Sc > Nb > Ga > Th > Y > Hf. Sulfurs, Pb, Sr, and Nd exhibited concentrations that exceeded geochemical background values. The analysis of the sediment quality indices allowed us to understand that the Nador lagoon was moderately to strongly polluted by heavy metals originating from various anthropogenic activities. Results from the Sediment Quality Guidelines indicated a toxic response in the benthic organisms within the lagoon, while the ecological hazard analysis revealed a very high risk of heavy metal contamination in the ecosystem. The Hazard Index for non-carcinogenic values was below the limit, suggesting a lack of non-cancerous effects. However, Cu and Pb concentrations surpassed the Lifetime Cancer Risk range, indicating a potential cancer risk with prolonged exposure. Integrating our research into coastal management frameworks can contribute to the preservation and enhancement of these coastal ecosystems for future generations.

The detachment and mobilization of boulders from rocky shore platforms by waves involves complex geomorphic and hydrodynamic processes. Understanding these processes requires precise information on the rates and patterns of movement of these megaclasts scaled against the wave conditions that generate boulder mobility. Repeat photogrammetry and structure-from-motion (SfM) models commonly used in geomorphic analyses are an interesting option for monitoring boulder dynamics. In this study, we used unmanned aerial vehicle (UAV)-based digital photogrammetry and SfM differential models to identify recent boulder movements over a rocky shore platform in Laghdira, Morocco. Combining these results with data on storm occurrence in the study area allowed us to identify storm waves as the unique driver of the dislodged and mobilized boulders. The identified storm event had a significant wave height of 5.2 m. The UAV models were built from imagery captured in September and December 2019 using a DJI MAVIC PRO PLATINUM, and we used QGIS to produce 2D and 3D model outputs. The exploitation of the 2D model differentials allowed us to appreciate the response of the boulders to the storm waves and to determine platform volumetric changes and, therefore, boulder mobility. The 3D models were valuable in determining the mode of transport of the boulders. Mobility patterns included sliding, overturning with no further mobility, and rotation and saltation, as well as boulder breakup. Storm waves did not have a preferential impact on any particular boulder shape, size category, or position at the outer edge of the platform. These results highlight the utility of combining UAV surveys with identified storm events, which are much more frequent than tsunamis, in determining observed boulder initiation and mobility.