Fatty Acid-Derived Metabolic Indicators and Biomagnification of Halogenated Organic Contaminants: A Comparative Analysis of Adjacent Coastal Predator-Based Food Webs.

Fatty acids (FAs) mediate trophic energy transfer and may reflect biochemical responses to contaminant exposure, yet their linkage with halogenated organic contaminants (HOCs) across adjacent coastal food webs remains unclear. This study comparatively examined the occurrence, biomagnification, and associations between 103 HOCs and 36 FAs in two predator-based food webs from the Pearl River Estuary: a marine fish-dolphin (Sousa chinensis) food web and a mangrove-associated terrestrial insect-spider (Nephila pilipes) food web. The fish-dolphin food web exhibited higher HOC biomagnification (BMFs < 489) and trophic magnification (TMFs < 5.19) than the insect-spider food web (BMFs < 2.78; TMFs < 3.08), although both showed similar biomagnification peaks at log KOW ≈ 7 and log KOA ≈ 11. Multivariate analyses identified 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153), 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), and a medium-chain chlorinated paraffin congener (C17H29Cl7) as contaminants most strongly associated with dolphin FA profiles, whereas 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), bis(2-ethylhexyl)-tetrabromophthalate (TBPH), and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT) were predominant contributors in spiders. HOC concentrations showed positive associations with saturated FAs in dolphins but negative associations with polyunsaturated FAs in spiders, and were significantly associated with FA-derived metabolic indices (R2 = 0.234-0.554, p < 0.05), including stearoyl-CoA desaturase 16 (SCD16) and stearoyl-CoA desaturase 18 (SCD18) in dolphins, and delta-6-desaturase (D6D) and de novo lipogenesis (DNL) in spiders. These relationships are correlative and likely reflect the combined influence of food-web characteristics, contaminant exposure, and species-specific physiology. This study provides a comparative assessment of HOC biomagnification and FA-derived metabolic indicators across contrasting predator-based coastal food webs.