The latitudinal variations in sedimentary molecular markers reveal broad-scale spatial patterns in organic matter sources and anthropogenic pressure across Norwegian fjords, NE Atlantic

This study presents a comprehensive latitudinal analysis of sedimentary molecular markers in Norwegian fjords, highlighting broad-scale spatial patterns in organic matter (OM) sources and anthropogenic influence along a south-to-north gradient. A multiproxy approach involving photosynthetic pigments, alkenones, polar steroids, n-alkanes, hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs) was applied to surface sediments from fjords located along a transect from the Skagerrak to northern Norway. Marine-derived OM showed no consistent trend in overall productivity with latitude, although changes in phytoplankton community structure were evident. Sterol markers revealed gradual shifts in the relative abundances of dinoflagellates and diatoms along the latitudinal gradient. Terrestrial contributions from vascular plants, indicated by long-chain n-alkanes, decreased markedly toward higher latitudes, consistent with regional vegetation transitions. Anthropogenic molecular markers (e.g., sewage steroids, hopanes, PAHs) declined sharply with latitude, with southern fjords exhibiting more distinct signatures of human impact, while northern fjords remained relatively pristine. Statistical analyses (PCA, linear regression) confirmed robust latitudinal gradients for multiple geomarkers. These findings demonstrate the utility of molecular markers in tracing OM sources and assessing environmental pressures across climatic and anthropogenic gradients. Understanding spatial variability in OM sources and anthropogenic influence is essential for evaluating environmental status in coastal marine ecosystems. This multiproxy-based study on latitudinal patterns of organic matter sources will help evaluate the impact of climate-driven shifts and, consequently, support projections of changes in carbon cycling.