<p>Organic carbon (OC) and mercury (Hg) are coupled in natural environments and have both been widely increasing in lakes of the northern hemisphere over the last decades. They would thus be expected to co-vary in lake sediments and to increase in recent sediments, but their anthropogenic drivers differ and are confounded with natural sources of variation; hence, their broad-scale patterns remain poorly understood. We measured the concentrations, accumulation rates and composition of Hg and OC in surface sediments of 25 lakes in two boreal regions spanning a 1000 km gradient in Quebec, Canada, and further obtained ~ 1m sediment records in two of these regions. Hg concentration increased with higher percent organic C (%OC) in the sediments and higher dominance of humic-like, terrestrial-derived dissolved organic matter in sediment porewater. Concentrations of OC and Hg in lake surface sediments tended to be higher in smaller and deeper lakes with higher concentrations of total Hg and nitrogen and lower oxygen saturation and pH in the lake water. Hg concentrations and accumulation rates were typically several folds higher in recent sediments, likely because of anthropogenic deposition. Recent accumulation rates were more pronounced and consistent for Hg than OC, suggesting an anthropogenic effect on sediment Hg accumulation in remote boreal lakes that is not as clearly expressed in terms of OC accumulation. Therefore, both elements may have distinct future trajectories in lake sediments in response to broad-scale environmental disturbances such as climate change and atmospheric pollution.</p>