The use of marine diesels in Arctic areas is expected to increase due to increased shipping transport, oil and gas activities, and the ban of heavy bunker oils in many areas. This project aimed at gathering information regarding the sensitivity of an Arctic copepod to marine diesel. The approach undertaken was to study the effects on survival (LC50s) and gene expression of a known detoxification gene (glutathione S-transferase [GST]) in Calanus glacialis following exposure to water soluble fractions (WSFs) of marine diesel (at 2 °C). We compared the observed LC-values of C. glacialis to the identical experimental data of the boreal Calanus finmarchicus (at 10 °C), and to the predicted LC50-values using regression models. The C. glacialis appeared more tolerant to the acute effects of marine diesel WSF compared to the "average pelagic crustacean" as predicted by regression models, and compared to C. finmarchicus. Although these results may be explained by a slower equilibration of petrogenic chemicals from the WSF at lower temperatures, C. glacialis also displayed higher GST expression following exposure than C. finmarchicus. In addition, the lipid content of the test organisms appears to be an important factor for the determination of acute toxicity, as copepods with high lipid content survived longer than copepods with low lipid content.