Effects of polycyclic aromatic hydrocarbons on oxidative responses in mangrove plants from Escravos Estuary and adjoining creeks, Nigeria
Date
2025Author
Onyena, A.P.
Manohar, C.S.
Suneel, V.
Nkwoji, J. A.
Chukwu, L. O.
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Mangrove ecosystems provide vital ecological services but face increasing threats from polycyclic aromatic hydrocarbon (PAH) contamination. This study examines PAH bioaccumulation and oxidative stress responses in mangrove plants from the Escravos Estuary and adjoining creeks, Nigeria, linking PAH contamination to biochemical stress markers. PAH concentrations in sediments, leaves, and roots were analysed using gas chromatography mass spectrometry (GC MS), while oxidative stress biomarkers malondialdehyde (MDA), superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT) were quantified. Mean total PAH concentrations (mg/kg) were 0.100 in sediments, 0.425 in leaves, and 0.736 in roots, with anthracene dominant in biological tissues. PAH contamination was more pronounced in mangrove tissues, suggesting higher bioavailability. Transfer factor analysis further revealed that high-molecular-weight PAHs were effectively taken up from sediments and translocated to leaves, indicating selective accumulation within mangrove tissues. PAH sources were predominantly pyrogenic at several stations (ML11, MR11, Sed11), while Station 4 consistently reflected mixed pyrogenic petrogenic inputs, indicating overlapping contamination from combustion and oil-derived activities. Elevated MDA levels and suppressed antioxidant enzymes indicated physiological stress. Risk quotient analysis identified contamination hotspots, emphasising the need for regulatory interventions and conservation measures to mitigate PAH-induced stress in mangroves.
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