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Biogeochemical processes in land-ocean interfaces, surface estuaries, subterranean estuaries and sediment-water interface
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Distribution patterns of nitrogen-cycling bacterial groups between pristine and human-impacted sites of coastal northern Bay of Bengal
Monday 7th @ 1430-1450, Conference Room 1
Anwesha Ghosh* , Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata
Punyasloke Bhadury, Integrative Taxonomy and Microbial Ecology Research Group, Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata
Presenter Email: anweshag91@gmail.com |
| Increased addition of nitrogenous compounds from land run-off into coastal oceans has been recorded since the industrial revolution. The process of remineralization of increasing concentrations of nitrogen in coastal oceans requires a better understanding of the resident bacterioplankton populations. Presence of specific nitrogen-cycling bacterial groups within the total bacterioplankton communities could act as proxy for changing nitrogen profiles due to human activities in coastal regions. Three pristine and three highly human-impacted coastal regions in northern Bay of Bengal were analyzed to understand the potential influence of increased nitrogen on bacterioplankton community structure. The three pristine regions representing low-nitrogen areas were Thakuran, Matla and Harinbhanga estuaries located with the Sundarbans mangrove ecoregion with an average dissolved nitrogen concentration of 29 µM. One site each from the Mooriganga estuary, Chemaguri Creek and Junput which are located in densely human populated areas served as high nitrogen areas with an average nitrogen concentration of 45 µM. The 16S rDNA V3-V4 region sequence data generated using next-generation sequencing was processed using QIIME and taxonomic affiliation was performed to elucidate the members of the bacterioplankton communities. This information was further used to predict abundance and type of nitrogen transporters harboured by these bacterioplankton. Interestingly, only 1% of the total bacterioplankton community from all studied stations showed affiliated with published sequences of Nitrospira, Lentisphaerae, Chloroflexi and Planctomycetes which are known to play a crucial role in nitrogen cycling. Correlation analysis did not show any direct relation between the dissolved inorganic nitrogen concentrations (dissolved nitrate and dissolved ammonium) with the abundance of nitrogen-fixing bacterioplankton. Incidentally, the abundance profile of surface expressed nitrogen (both nitrate and ammonium) uptake transporter systems showed a gradual decline from low to high nitrogen sites. This indicated the possible presence of greater abundance of high-affinity nitrogen transporters in the low-nitrogen areas. Such observations involving abundance and functional level information on members of bacterioplankton communities could become crucial in understanding ecosystem level processes such as nitrogen cycling in coastal regions.
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