Using ‘n-alkane’ Proxy to Understand the Fate of In-situ Organic Matter in Mangrove Sundarban Delta and its Relation to Delta Carbon Budget

Saini, Jeetendra Kumar (2014) Using ‘n-alkane’ Proxy to Understand the Fate of In-situ Organic Matter in Mangrove Sundarban Delta and its Relation to Delta Carbon Budget. Masters thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

n-Alkanes are important and robust lipid biomarker proxy to understand different biogeochemical processes. There’s very little known about how the bacteria influence the distribution, abundance and C-isotopic composition of n-alkanes in sedimentary archives after their production by different kind of plants. Sampling was performed in the Mangrove Sundarban area in Bakkhali, West Bengal, India. n-alkane degrading bacteria were isolated by enrichment in a Standard M9 Minimal medium, with providing three different n-alkane source of carbon i.e., short chain n-alkane (C8-C24), long chain n-alkane (C24-C-35) and Mix (C8-C40). The isolated strains were characterized by biochemical tests and identified by amplification of 16S r-DNA sequencing. The bacteria capable of degrading short and long chain n-alkanes were found to be related to 'Acinetobacter junii’ after their 16S r-DNA sequencing. Using above isolates we then performed 14 days quantitative controlled n-alkane degradation experiment by growing them in M9 minimal medium and using alkane calibration standard n-alkane (C8-C40) from Sigma Aldrich as only carbon source having a uniform odd and even n-alkane concentration. The n-alkane concentration data after degradtion show that for short chain n-alkanes from C11 to C21 there is even over odd predominance (EOP), while for long chains its odd over even predominance (OEP). There is abrupt rise in odd carbon chain preference between C21 to C25 n-alkane chain lengths. The above experiments suggest that n-alkane degrading bacteria preferably degrade short chain even n-alkanes and thus pose limited effect on the long chain n-alkanes those are used for the various paleoclimate reconstructions.

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