Mangrove ecosystems are rich repositories of diverse microbial communities which mediate various biogeochemical processes and reactions. However, phylogenetically divergent lineages coexisting in mangrove habitats may respond differently to local environmental characteristics. Hence, it is important to understand their composition, community structure, diversity with respect to pertinent controlling environmental factors. We investigated seasonal down-core variations in bacterial communities at 3 mangroves sites along the economically-important Mandovi estuary, west coast of India. Sediment cores collected from Volvoi (upstream), Chorao (mid-stream) and Betim (mouth) during pre-monsoon, monsoon and post-monsoon seasons were sectioned at 5 depth intervals i.e. 0-1, 3-4, 6-8, 10-11 and 14-15 cm. Genomic DNA extracted from 45 sediment samples were analyzed by 454 pyrosequencing.