Screening pollution biomarkers and burrowing population profiles in an infaunal key species from port estuarine areas: What does deeper sediment say?

Abstract

Port-related activities represent a source of many pollutants, including trace elementsand Polycyclic Aromatic Hydrocarbons (PAHs) that could be sequestered indeeper estuarine sediments. We evaluated whether a key infaunal bioturbator, the nereidid Laeonereis acuta, integrates exposure to contaminants deposited below the surface. During austral summer we sampled port and non-port sites in three Buenos Aires estuaries—Samborombón (SAM), Quequén Grande (QQG), and Bahía Blanca (BBL)—collecting surface (0–10 cm), middle (10–20 cm), and deep (20–30 cm) sediments for trace elements and PAHs, and assayed polychaete biomarkers (CAT,SOD, GST, SH-g, TBARS, TAC, HSP70, NKA, LDH, LYS), integrated with PCA and Integrated Biomarker Response (IBR). We also quantified densities, cohort structure,and burrowing profiles. Port sites exhibited higher burdens of Cd, Hg, As, Cu and several PAHs—often exceeding sediment quality guidelines—especially in middle and deep layers; diagnostic ratios indicated mainly petrogenic sources in ports. Biomarker profiles differed consistently between port and non-port areas: QQG-port showed elevated CAT and HSP70; BBL-port showed increased TAC, SH-g, and GST with SOD and NKA inhibition; TBARS increased at SAM and BBL ports. IBR separated stress gradients both within and among estuaries, with the highest values at the BBL-port. Population endpoints mirrored sub-individual signals: lower densities, limited recruitment, and shallower depth use at BBL, while adults elsewhere reached >20 cm, indicating potential exposure to buried contamination. Our findings revealed that deeper sediments substantially shape exposure and effects, and that combining multibiomarker and population metrics when using infaunal benthic species as bioindicators offers a sensitive tool for port-estuary monitoring.