Assessing the ecological health risk in a conserved mangrove ecosystem due to heavy metal pollution: A case study from Sundarbans Biosphere Reserve, India

ABSTRACT

Sundarbans Biosphere Reserve (SBR) is the world's largest contiguous conserved mangrove forest with unique flora and fauna, but it still has to bear the brunt of anthropogenic disturbances due to huge population pressure. This study aimed to identify the sources, extent of metal pollution (Cd, Cr, Mn, Ni, Pb, and Zn), and their potential ecological risk in this fragile ecosystem. Sediments were collected from 10 locations with varied levels of anthropogenic pressure from the fringe of the reserve forest. Cluster analysis (CA) and factor analysis (FA) identified Ni, Cd, and Pb as the major anthropogenic pollutants in this area. Concentrations of Pb (27.79–47.07 mg/kg) and Cd (0.8–3.3 mg/kg) were found to be higher in areas reliant on fossil fuel-operated motorboats for transport and dependent on rechargeable batteries to cope with the shortage of electricity. The contamination factor (C_f), geoaccumulation index (I_geo), and ecological risk index (ERI) highlight that populated areas are mostly exposed to Cd, Pb, and Cr contamination. Interpolation maps identified that the central part of the area is acutely affected by Cd pollution, whereas the main ecotourism routes within the reserve forest have high Pb concentrations. This study concludes that conservation-friendly ecotourism and improper disposal of batteries can also pose a threat to this ecosystem and these possibilities could be considered during formulation of conservation plans.

KEYWORDS:

• ecological risk index
• mangrove conservation
• contamination factor
• principal component analysis
• ecotourism

Acknowledgments

The authors are indebted to Shantanu Bhattacharryya, Programme Coordinator at Tagore Society for Rural Development, Rangabelia Project for helping in the fieldwork and enduring the harsh monsoon rains, cyclonic surges in launch and surviving intense summer heat to aid in sample collection. The authors also acknowledge the help provided by Aliya Naz, Research Scholar, Indian School of Mines, Dhanbad for editing the manuscript.

Funding

A. Chowdhury is thankful to the Indian School of Mines, Dhanbad, and Ministry of Human Resource Development, India, for providing the fellowship to conduct this study.