Accumulation patterns of polychlorinated alkanes in an Arctic marine food web

Polychlorinated alkanes (PCAs), otherwise known as chlorinated paraffins, are contaminants of emerging Arctic concern where our understanding of their occurrence and trophic transfer in Arctic food webs remains limited. To investigate biomagnification potential of PCAs, we analyzed short-chain PCAs: C₁₀-C₁₃ and medium-chain PCAs-C_14-17 in three Arctic species: polar cod (Boreogadus saida), ringed seal (Pusa hispida), and polar bear (Ursus maritimus) and Subarctic capelin (Mallotus villosus) samples collected from the northern Barents Sea in 2017 and 2021. PCAs-C_10-13 concentrations were low, but detectable in all species, while PCAs-C_14-17 concentrations were mainly below detection limits in the mammals. PCAs did not biomagnify, as the lowest concentrations were found in polar bear (0.7 ng g^-1 lw) and the highest in capelin (56.9 ng g^-1 lw). The PCA homologue profiles were similar among Arctic species, with PCAs-C_10-13 dominating in polar cod and marine mammals, which may suggest a contribution from long-range atmospheric transport. In contrast, PCAs-C_14-17 were most abundant in the Subarctic capelin, likely reflecting a different exposure. Despite differing PCAs-C_14-17 concentrations among the two fish species, their PCAs-C_14-17 homologue profile was similar, indicating uniform global production trends. Subarctic capelin is increasingly being preyed upon by Arctic predators and may facilitate the biological transport of PCAs-C_14-17 into Arctic ecosystems. These findings suggest that climate-driven shifts in species distribution may have the potential to alter contaminant exposure pathways in Arctic marine food webs.