Abstract

In the Sundarban Mangrove forest, microbial activities are dominantly involved both in the mineralization and decomposition processes that regulate nutrient profile of sediment of different depth. It was found that besides changing the water and sediment quality, monsoonal cycle plays a crucial role to regulate microbial population distribution in the mangrove sediment. Statistical analysis revealed that organic carbon was the most significant factor that regulates the total microbial population. The cellulose degrading bacteria, [mean value of CFU 14.320×10⁶ (gm dry weight of sediment)^-1] was dominant throughout the year. The sulphate reducing bacteria showed an increasing trend along depth with a minimum value at the surface that is 6.113×10⁶ (g dry weight of sediment)^-1and 12.312×10⁶ (g dry weight of sediment)^-1 at a depth of 60 cm. Both rooted and deep mangrove forest regions showed distinct stratification of microbial population and nutrient distribution whereas the un-rooted regions did not show any such stratification which may be attributed to frequent wave and tidal action that make it a higher energy zone. Intensification of monsoonal cycle could heavily affect microbe dominated sediment biogeochemistry and subsequent change in the regional ecology of Sundarban mangrove forest. 

Key words: Sundarban Mangrove, microbial population, monsoonal cycle, nutrient concentration.