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Anthropogenic environmental stressors (like atmospheric deposition, land use change, and climate warming) are predicted to increase inorganic nitrogen and organic carbon loading to northern boreal lakes, with potential consequences for denitrification in lakes. However, our ability to predict effects of these changes is currently limited as northern boreal lakes have been largely neglected in denitrification studies. The aim of this study was therefore to assess how maximum potential denitrification and N₂O production rates, and the relationship between the two (relative N₂O production), is controlled by availability of nitrate (NO₃⁻), carbon (C), phosphorus (P), and temperature. Experiments were performed using the acetylene inhibition technique on sediments from a small, nutrient poor boreal lake in northern Sweden in 2014. Maximum potential denitrification and N₂O production rates at 4°C were reached already at NO₃⁻ additions of 106–120 μg NO₃⁻–N/L, and remained unchanged with higher NO₃ amendments. Higher incubation temperatures increased maximum potential denitrification and N₂O production rates, and Q10 was somewhat higher for N₂O production (1.77) than for denitrification (1.69). The relative N₂O production ranged between 13% and 64%, and was not related to NO₃⁻ concentration, but the ratio increased when incubations were amended with C and P (from a median of 16% to 27%). Combined, our results suggests that unproductive northern boreal lakes currently have low potential for denitrification but are susceptible to small changes in NO₃ loading especially if these are accompanied by enhanced C and P availability, likely promoting higher N₂O production relative to N₂.