Bioaccumulation and translocation of heavy metals in mangrove rhizosphere sediments to tissues of Avicenia marina - A field study from tropical mangrove forest

Samples of rhizosphere sediment, plant tissues like branch, bark, root, leaf and stem of Avicenia marina were collected from the Muthupet mangrove forest and analyzed for heavy metal (Cu, Cd, Pb and Zn) accumulation and translocation. The results showed that the samples of A. marina have increased concentration of heavy metals especially, the non essential metals like Cd and Pb. Also, seasonal influence occurred during the accumulation of metals, among them summer and postmonsoon recorded as more contaminated season. The essential metals like Cu and Zn were found higher in rhizosphere sediment of A. marina when compared with non essential metals. Thus the plant was rapidly utilizing Cu and Zn for their active metabolism. The accumulation and translocation of Cu and Zn were lesser than the concentration scaled by WHO. High Bioaccumulation factors (BAFs) and Translocation factor were observed for Cd and Pb. The recorded values of metal in rhizosphere sediment and plant tissue were below the sediment quality guideline and upper critical limit of metals in plant. However, the values of present study several fold higher than the previously reported studies from the study area, which confirmed that extended anthropogenic activity takes place in the study area. These findings provide actual and reliable data on heavy metal accumulations and translocation in rhizosphere sediment to plant tissues of A. marina from Muthupet mangrove ecosystem, further long-term management and conservation policies are needed to protect the ecosystem.