Coastal hydrodynamics and anthropogenic activities drive mineralogical-geochemical spatial patterns and foraminiferal assemblages in the northern Gulf of St. Lawrence (eastern Canada)

This study investigates the sedimentological, mineralogical, geochemical, and foraminiferal characteristics of three coastal zones in the northwestern Gulf of St. Lawrence: (1) Port-Cartier, (2) the Bay of Sept-Îles (BSI), and (3) Matamec. Sediment samples were analyzed for grain size distribution, mineral and geochemical composition, and benthic foraminiferal assemblages. The results reveal notable spatial variability influenced by local geology, hydrodynamic conditions, and anthropogenic activities. High-energy hydrodynamic conditions at Port-Cartier and Matamec result in predominantly coarse-grained sediments, while variable energy regimes in the BSI produce a heterogeneous mixture of fine and coarse materials. Mineralogical analyses indicate that Port-Cartier and Matamec sediments are rich in quartz, K-feldspar, and amphibole, originating from local granitoid and metamorphic bedrock and are transported northeastward, or westward in case of Matamec by tidal currents. BSI sediments are markedly enriched in iron and organic matter, due to natural geological inputs amplified by anthropogenic activities, particularly in areas influenced by industrial discharge and anticyclonic circulation. Foraminiferal analyses reveal distinct community patterns closely correlated with sedimentological and geochemical variations. Calcareous species, sensitive to elevated metal concentrations, are largely absent in the BSI, where agglutinated foraminifera dominate iron-rich, fine-grained environments. Foraminiferal populations are also sparse or absent near active river deltas and in gravel-rich substrates, reflecting harsh physical conditions, substrate instability, and fluctuating salinity. Ecological indices exp(H’ bc ) and Foram-AMBI further highlight the sensitivity of foraminiferal assemblages to both natural sediment characteristics and subtle anthropogenic stressors. As the first comprehensive foraminiferal study in this region, this research provides essential baseline data and identifies sensitive bioindicators for long-term ecological monitoring, meaningfully advancing our understanding of sedimentary processes and ecological responses to environmental stress in northern coastal ecosystems. • Hydrodynamic regimes across Port-Cartier, the Bay of Sept-Îles (BSI) and Matamec control foraminiferal distribution. • Elevated metal and organic concentrations in the BSI reflect natural and potential anthropogenic sources. • Stress-tolerant agglutinated foraminifera dominate the BSI, where calcareous taxa are absent. • First integrated foraminiferal, sediment, geochemical study provides baseline data for the region.