To test how environmental conditions in the Arctic and the resulting ecological adaptations affect accumulation of persistent organic pollutants (POPS) in the marine food web, bioaccumulation of four polychlorinated biphenyls (PCBs) in an arctic (Barents Sea 77 degrees N-82 degrees N) and a temperate marine (Baltic Sea 54 degrees N-62 degrees N) food web were compared Three different trophic levels were studied (zooplankton. fish, and seal), representing the span from first-level consumer to top predator. Previously published high-quality data on PCB water concentrations in the two areas were used for calculation of bioaccumulation factors (BAF) BAF was calculated as the ratio of the PCB concentration in the organism ([PCB](org); pg/kg lipid) to the dissolved water concentration (C-w, pg/L). The BAF(Arctic):BAF(Temperature) ratios were above 1 for all four PCB congeners in zooplankton (6.4-138) and planktivorous fish (2.9-5.0)), whereas the ratios were below 1 in seal The mean ratio between arctic and temperate BAFs for all trophic levels and congeners (BAF(Arctic) BAF(Temperate)) was 4.8. When the data were corrected for the seawater temperature difference between the two ecosystems, the ratio was 2 0 We conclude that bioaccumulation differences caused by ecological or physiological adaptations of organisms between the two ecosystems were well within a water concentration variability of 50%. Further, our data support the hypothesis that lower seawater temperature lead to a thermodynamically favoured passive partitioning to organic matrices and thus elevated ambient BAFs in the Arctic compared to the Baltic Sea This would imply that bioaccumulation in the Arctic may be described in the same way as bioaccumulation in temperate regions. e g by the use of mechanistic models parameterised for the Arctic. (C) 2010 Published by Elsevier B.V.