Diversity of epiphytic lichens and their role in sequestration of atmospheric metals

Diversity and abundance of five species of epiphytic lichens were assessed in Kolkata, India. Signifi- cant correlation between abundance of lichen species and volume of vehicular traffic suggests atmospheric pollution load in urban region. Parmelia caperata (L.) Ach. and Graphis scripta (L.) Ach. exhibited higher abundance among the five species studied indicating their higher level of tolerance to air pollution. Significant correlations (p \ 0.05) between levels of heavy traffic and both diver- sity and abundance of all lichen species were also observed. These findings indicate a potential threat to the survival of the lichen communities in Kolkata. Study fur- ther deals with quantifying the effectiveness of lichen species in accumulating metallic elements like Pb, Zn, and Cu. This was achieved by analyzing the most abundant lichen species (Parmelia caperata) collected from nine different sites in winter, summer, and monsoon seasons. Metal content in lichen thalli, as analyzed by AAS, shows their elevated levels with the order Pb ( Zn ( Cu. Rela- tionship between metal content and volume of vehicular traffic suggests that co-associated, metallic elements are emitted as vehicle-derived pollutants as well as diffuse industrial emissions. Accumulation of these metals is higher in winter which is proportionate with the higher degree of metabolism due to higher humidity in this sea- son. Study also demonstrates the dynamics of metal uptake by the lichen at different sites influenced with different degree of vehicular traffic. Overall results confirm suit- ability of lichen with their potential role in sequestration of atmospheric metal contamination.