Microbial Ecosystem in Sunderban Mangrove Forest Sediment, North-East Coast of Bay of Bengal, India

Abstract

This is the first documentation of seasonal and spatial fluctuation of the culturable microbial population collected from different zones in the sediment of the Sunderban mangrove forest. The population of cellulose degrading bacteria, [mean value of CFU 6.189 ± 1.025 × 10⁶ (g dry weight of sediment)⁻¹] was found to be maximum during post monsoon in the deep forest region, whereas, the fungal population [mean value of CFU 3.424 ± 0.886 × 10⁶ (g dry weight of sediment)⁻¹] was found to be maximum during pre-monsoon in the rooted region. The abundances of microbes, in decreasing order, studied from different zones are nitrifying bacteria [mean value of CFU 1.125 ± 0.359 × 10⁶ (g dry weight of sediment)⁻¹], phosphorous solubilizing bacteria (PSB) [mean value of CFU 0.805 ± 0.322 × 10⁶ (g dry weight of sediment)⁻¹], free living nitrogen fixing bacteria [mean value of CFU 0.417 ± 0.120 × 10⁶ (g dry weight of sediment)⁻¹] and sulfur reducing bacteria (SRB) [mean value of CFU 0.356 ± 0.125 × 10⁶ (g dry weight of sediment)⁻¹]. The content of organic carbon in the soil decreased from the deep forest region to the rooted and unrooted region but a reverse profile was found for soil salinity and soil silicate concentration. The results from the present study indicate that the monsoon cycle has a pronounced effect on the microbially dominated biogeochemistry in the sediment and consequently on the ecology of the Sundarban mangrove forest.

Keywords:

• monsoon
• microbial community
• nutrients
• physicochemical parameters
• sundarban mangrove forest

Acknowledgments

The financial assistance from DST, New Delhi, Govt. of India and Department of Environment, Govt. of West Bengal, are gratefully acknowledged. The authors are also grateful to the Forest Department, Govt. of West Bengal for assisting the research team in collecting data and providing all infrastructural facilities to reach the remote island.