Identification of metal tolerant plant species in mangrove ecosystem by using community study and multivariate analysis: a case study from Indian Sunderban

This study at Indian Sundarbans, identifies metal tolerant mangroves with phytoremediation potential by understanding the affect of metal pollution on the community structure of this estuarine ecosystem. Community study indicates that polluted site has lower relative density of the true mangrove and four metal tolerant species (Cryptocoryne ciliata, Heliotropium currasavicum, Hemarthria altissima and Avicennia officinalis) are predominant with 72 % of relative density. Biodiversity indices (Simpson's index of Dominance and Diversity, Shannon-Weiner index) indicate reduction in diversity and increase in dominance of metal tolerance species at the polluted site. The cluster/components originating after cluster and principal component analysis shows that Cr, Pb, Cd and Ni are metal pollutants of anthropogenic origin. Metal accumulation study is conducted on these four species after assessing the status of metal pollution in their rhizospheres using Ecological risk index, Geoaccumulation index, Enrichment factor and Contamination factor. Bioaccumulation factor emphasized that C. ciliata has a high potential for extracting Cd, Cr and Pb. Bioconcentration factor of Cr is high for A. officinalis, C. ciliata (potentially invasive) and H. altissima (invasive species) whereas translocation factor indicates Cd, Ni and Zn can be translocated to the aerial part of these plants. In addition, H. altissima also transfer Cr and Pb to their aerial parts. This study concluded that C. ciliata could be used as phytoextracter for Cd, Cr and Pb in metal contaminated mangrove ecosystem.