Bioaccumulation and Trophic Transfer of Phthalate Esters in the Food Webs of Jinpu Bay, China: Health Risks Assessment for Spotted Seals

Phthalate esters (PAEs) are ubiquitous in aquatic environments and pose biotic risks, but their bioaccumulation and trophic transfer mechanisms across full coastal marine food webs remain poorly characterized. This study investigated PAEs in the Jinpu Bay (China) food web, encompassing seawater, sediments, and biota from plankton to marine mammals (e.g., spotted seals). Σ₆PAE concentrations were 341.9–811.1 ng/L (seawater), 150.8–247.2 ng/g dry weight (sediments), and 1611.6–73880.7 ng/g lipid weight (biota), with dimethyl phthalate (DMP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) as the dominant congeners. Log-transformed bioaccumulation and biota-sediment accumulation factors (log BAFs, BSAFs) were below thresholds, indicating limited bioaccumulation potential. Trophic analysis based on two constructed food webs with distinct structures revealed a nonlinear, ecosystem-dependent pattern between PAE concentrations and trophic levels (TLs): Food Web 1 (TL ≈ 1.5–3.5) exhibited trophic dilution (trophic magnification factor, TMF < 1), whereas Food Web 2 (TL ≈ 3.0–4.0) showed trophic magnification (TMF > 1). These patterns were driven by hydrophobicity, food chain length, species composition, and metabolic capacity of higher-TL organisms. In Food Web 2, DBP and DEHP exhibited exceptionally high TMFs (6.52 and 9.91, respectively), indicating strong biomagnification potential at upper TLs. However, dietary PAE exposure posed low health risks to spotted seals, with hazard quotients (HQs) of all PAE congeners < 0.01. This study elucidates the complex trophic dynamics of PAEs, thereby providing critical insights for ecological risk assessmen