Caribbean coral reefs face rising pressure from coastal development, yet the pathways by which urban pollution reaches these endangered ecosystems remain poorly understood. Bays act as dynamic channels, trapping, transforming, and releasing materials that can impact adjacent reef systems. We investigated the seasonal and spatial variability of suspended particulate matter (SPM)—a key vector for pollutants and nutrients— coming from an urbanized bay in Curaçao and determined its effect on surrounding coral reefs. Using sediment traps deployed across spatial gradients (bay mouth to nearby reefs in the East and West) during the dry (April–May) and wet (October–November) seasons, we measured mass, carbon, and nitrogen fluxes and associated grain-size and geochemical particle composition. Results were compared to environmental conditions (e.g. rain fall, current speed) and revealed a clear spatial gradient of bay influence: the bay mouth showed the strongest terrestrial signal, followed by the eastern reef (sheltered from currents) with elevated SPM fluxes of fine particles enriched in terrigenous elements (Si, Fe, Al, and Mn), while the western reef (exposed to open-ocean flow) exhibited lower fluxes of coarser particles with elevated Ca/Fe, Pb, Cu and Ni. This indicates diminished bay effect and stronger marine influence mixed with localized pollution. During the dry season, differences in SPM fluxes and composition between reef sites were minimal, but wet season conditions amplified spatial patterns, with rainfall-driven runoff locally increasing dissolved and particular matter delivery. This implies that reef vulnerability to bay-derived pollution locally depends on both proximity to source waters and seasonal hydrodynamic variability, with sheltered reefs experiencing the greatest impacts during periods of enhanced terrestrial runoff.