10.18710/1GXLKB Andvik, Clare Clare Andvik https://orcid.org/0000-0002-1870-7106 University of Oslo DataverseNO 2026 Earth and Environmental Sciences Medicine, Health and Life Sciences isotopic niche biomagnification bioaccumulation biotransformation homeotherms ectotherms top predator emerging contaminants trophic enrichment chlorinated paraffins trophic dilution trophic magnification University of Oslo University of Oslo Andvik, Clare Clare Andvik University of Oslo Fagerlund, Carl Carl Fagerlund Jourdain, Eve Eve Jourdain Yuan, Bo Bo Yuan Haddad-Weiser, Gabrielle Gabrielle Haddad-Weiser Lyche, Jan Ludvig Jan Ludvig Lyche Karoliussen, Richard Richard Karoliussen Ruus, Anders Anders Ruus Borgå, Katrine Katrine Borgå 2026-03-18 2026-08-03 Field data; Modelling data 10.1016/J.ENVRES.2026.125367 10.18710/1GXLKB/CNTDQK 10.18710/1GXLKB/QV4CIX 10.18710/1GXLKB/ZAHWNB 98809 308577 7492 text/x-r-notebook text/plain text/plain 1.0 Creative Commons CC0 1.0 Universal Public Domain Dedication. Polychlorinated n- alkanes (PCAs), the largest component of the commercial product chlorinated paraffins, have been used globally in increasing amounts since the regulations of legacy persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs). The bioaccumulative potential of PCAs compared to legacy contaminants is inconclusive, with limited data available for PCAs with carbon chain length ≤ 9 and ≥ 18, particularly in food webs which include mammalian top predators. Here, we analysed and compared PCAs of different carbon chain length (very-short: PCAs-C6-9 [vSCCPs], short: PCAs-C10-13 [SCCPs], medium: PCAs-C14-17 [MCCPs], and long: PCAs-C18-24 [LCCPs]), 57 legacy POPs, and total mercury (Hg) in killer whales (Orcinus orca) from northern Norway (n = 59) and a range of fish and marine mammals. We found the physiological group of a species (homeotherm or poikilotherm) significantly influenced the tropic magnification factors (TMFs) of contaminants, with TMF estimations underestimated in PCAs and overestimated in legacy contaminants if unaccounted for. We found low trophic magnification in poikilotherm and homeotherms in shorter chained PCAs with TMF in PCAs-C6-9 2.1 [95% confidence interval: 0.9–4.8] and in PCAs-C10-13 2.4 [1.0–5.7]. In PCAs-C14-17 and PCAs-C18-24 we found high TMFs in poikilotherms (4.8 [1.3–1.8] and 4.6 [1.2–18], respectively) and no evidence of trophic magnification in homeotherms (1.0 [0.5–2.3] and 1.0 [0.4–2.8], respectively). Legacy POPs dominated in concentration and pattern in marine mammals (54–87%), whereas PCAs and Hg dominated in fishes (58–98%). Our results indicate higher PCA concentrations and biomagnification potential in poikilotherms than homeotherms, which is likely due to lower biotransformation and elimination ability. Norway Research Council of Norway 315392