Bioaccumulation and trophic transfer of phthalate esters in the food webs of Jinpu Bay, China: Health risks assessment for spotted seals.

Abstract

Phthalate esters (PAEs) are ubiquitous in aquatic environments and pose biotic risks, but their bioaccumulation and trophic transfer mechanisms across coastal food webs remain poorly characterized. We investigated PAEs in Jinpu Bay (China) food webs, encompassing seawater, sediments, and biota from plankton to air-breathing marine mammals. Σ₆PAE concentrations were 341.9-811.1 ng/L (seawater), 150.8-247.2 ng/g dry weight (sediments), and 1611.6-73,880.7 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 factors (log BAFs <3.7) and biota-sediment accumulation factors (BSAFs <1) were below established criteria, 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, comprising plankton to fish) exhibited trophic dilution (trophic magnification factor, TMF < 1), whereas Food Web 2 (TL ≈ 3.0-4.0, dominated by mid-to-high-TL taxa) 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 at upper TLs. However, dietary PAE exposure posed low health risks to spotted seals, with hazard quotients (HQs) of all PAE congeners <0.01. Notably, metabolite-related risks were not quantified, and long-term monitoring of high-TL predators is still warranted. This study elucidates the complex trophic dynamics of PAEs and provides critical insights for ecological risk assessment.