Sedimentary PAH and oxidative stress biomarkers responses on Namalycastis abiuma (Polychaeta: Nereididae) from an urbanized Amazon estuary

Abstract

Contamination by polycyclic aromatic hydrocarbons (PAH) in sediments and oxidative stress biomarkers responses (glutathione-S-transferase activity—GST and lipoperoxidation—LPO) on the polychaetes Namalycastis abiuma were screened along the urbanized margin of the Guajará Estuary, Brazilian Amazon coast, during dry and rainy seasons. Total 16 priority PAH concentrations ranged from 17 to 386 ng g−1 dry sediment, with higher values during the dry season. High molecular weight PAHs predominated during dry season and were probably originated from fossil fuel burning. Increased naphthalene and anthracene concentrations were noted when the maximum river flow was recorded and suggest diffuse sources from drainage of contaminated surfaces. Ecotoxicological PAH risks were low according to international sediment quality indices. Nevertheless, PAH toxicity equivalency was around 10-fold higher nearer the oil terminal than alongside the estuary. Highest GST activities at the oil terminal and industrial sites coincided with the rainy season, and combined with hydrochemical and sedimentary conditions thought to promote PAH bioavailability and a prolonged toxicant exposure. LPO approached similar levels in both seasons, suggesting that enzymatic activities were sufficient to uphold the prooxidants exposure. This result indicates that the overall estuarine condition exerts subtle oxidative stress on a keystone species and matches the low PAH ecotoxicological risks. Depositional margins within the mangrove areas and port operation are susceptible to an enhanced PAH accumulation and need special surveillance.