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Abstract
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Phthalate esters (PAEs) are widely used plastic additives continuously released into marine environments, yet
biologically mediated partitioning and sediment–biota coupling in semi-enclosed industrial basins remain
insufficiently quantified. This study presents an integrated multi-matrix assessment of six priority PAEs (DMP,
DEP, DBP, BBP, DEHP, DnOP) in seawater, plankton, and surface sediments from the northern Persian Gulf,
comparing a petrochemical-dominated coastline (Assaluyeh) with an urban shoreline (Bushehr) across cold and
warm seasons. Total PAE concentrations (ΣPAEs) followed a consistent matrix-dependent hierarchy: sediment >
plankton > > seawater (Kruskal–Wallis, p < 0.001; ε2 ≈ 0.88). Sediment concentrations reached 59.00 ng g− 1 dw
in warm-season Assaluyeh, while plankton ranged from 16.80 to 30.60 ng g− 1 dw and seawater from 0.325 to
0.597 ng L− 1
. Warm-season levels were significantly elevated across matrices (p = 0.029), coinciding with
increased plankton lipid content (up to 16.52%) and higher sediment TOC (up to 1.93%). Biota–water bioaccumulation factors (BAFs) were on the order of 104
–105 L kg− 1
, confirming lipid-driven enrichment of hydrophobic congeners, particularly DEHP (~41% of ΣPAEs) and DBP (~22%). In contrast, lipid- and TOCnormalized biota–sediment accumulation factors (BSAFs) were close to unity, indicating near-equilibrium partitioning rather than trophic magnification. Strong plankton–sediment correlations (ρ = 0.84, p < 0.001) support
biologically mediated vertical transfer. These findings highlight the critical role of plankton in regulating
contaminant redistribution in semi-enclosed industrial seas, with implications for bioavailability, benthic
exposure, and sedimentary accumulation of PAEs. The results provide a framework for improving coastal
monitoring in rapidly industrializing marine regions.
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