The construction of coastal infrastructure in sediment-limited arid environments can trigger substantial and spatially asymmetric shoreline responses with cascading ecological consequences. This study investigates the morphodynamic and ecological impacts of the Port of N’Diago in Mauritania between 2000 and 2025 by integrating high-resolution satellite imagery and Digital Shoreline Analysis System (DSAS) metrics. A total of 210 transects were established along a 20 km coastal segment—10 km north and 10 km south of the port—to quantify shoreline changes through Net Shoreline Movement (NSM), Shoreline Change Envelope (SCE), End Point Rate (EPR), and Linear Regression Rate (LRR). The analysis revealed a pronounced north–south asymmetry in shoreline dynamics: severe erosion occurred south of the port (maximum LRR −18.12 m·yr⁻¹), while significant accretion was observed to the north (maximum LRR +8.82 m·yr⁻¹), indicating a disruption of natural longshore sediment transport and the establishment of a polarized morphodynamic regime that challenges conventional equilibrium-based coastal models in arid systems. Ecological consequences were assessed by analyzing 80 marine turtle strandings spanning five species, including loggerhead (Caretta caretta), green (Chelonia mydas), hawksbill (Eretmochelys imbricata), leatherback (Dermochelys coriacea), and olive ridley (Lepidochelys olivacea). Strandings were significantly more frequent near the port, with green turtles accounting for 40% of records. One-way ANOVA revealed a significant effect of port proximity on stranding frequency (F(1,78) = 7.290, p = 0.008; η² ≈ 0.085), confirmed by Welch’s robust test (F(1,24.25) = 5.948, p = 0.022), and a Generalized Linear Model using a Poisson distribution further validated this positive association (p < 0.05), providing convergent evidence across parametric, robust, and distribution-adapted analyses. These results demonstrate a direct, quantitative link between engineered shoreline modifications and localized biological impacts, highlighting both the spatial magnitude of port-induced sediment redistribution and its ecological consequences. Limitations include the focus on a single port and arid coastal context, but the methodology offers transferable tools for assessing infrastructure-driven coastal change. The study provides original empirical evidence of how port development can reshape coastal morphodynamics and affect marine biodiversity, offering critical insights for coastal planning, habitat management, and conservation strategies in arid shoreline systems.