Bioaccumulation pattern of heavy metals in Avicennia marina at Visakhapatnam and Coringa mangroves in India

This study explores the impact of heavy metal accumulation on Avicennia marina's physiological and anatomical aspects, focusing on its capacity for metal uptake and tolerance. Conducted across the Visakhapatnam Entrance Channel (VEC) field, Control Coringa mangroves, and controlled ex-situ greenhouse environments, the study examines the accumulation patterns of chromium (Cr), lead (Pb), and cadmium (Cd). The Potential Ecological Risk Index (RI) indicated that Cd posed a very high risk, with Cr and Pb also showing significant risks. Heavy metal concentrations in the VEC from Cr (36.58–76.41 µg/g), Mn (209.19–428.8 µg/g), Cu (29.91–45.56 µg/g), Zn (306.44–925.16 µg/g), Cd (2.49–4.65 µg/g), and Pb (42.0–155.64 µg/g). The potential ecological risk coefficient Eir consistently placed Cd in the high-risk category, with other metals generally in low to moderate-risk categories. Physiological changes in plant tissues were analyzed using a fluorescence microscope, and higher metal concentrations were assessed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The Bioconcentration Factor (BCF) and Translocation Factor (TF) were calculated to evaluate metal accumulation and translocation efficiency. In VEC, significant anatomical changes in Avicennia marina included moist leaves, expanded mesophyll areas, and thick cuticles with heavy metal deposits, especially in high metal concentrations. The region's pollution, driven by port activities and nearby industries, elevated heavy metal levels in sediments. Cd was identified as a very high-risk element at all stations, while other metals were categorized under low or moderate risk. Comparative analysis with the Control Coringa mangroves indicated potential variations in metal accumulation strategies between the two regions within the same species. Anatomical changes in the VEC were more pronounced than fewer disruptions in Coringa mangroves, suggesting differential adaptive responses to environmental stressors. This study underscores the need for targeted environmental management strategies to mitigate heavy metal contamination and highlights the importance of maintaining healthy mangrove habitats amidst increasing anthropogenic pressures.