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Manganese cycling and its implication on methane related processes in the Andaman continental slope sediments

DRS at CSIR-National Institute of Oceanography

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Title Manganese cycling and its implication on methane related processes in the Andaman continental slope sediments
 
Creator Sujith, P.P.
Gonsalves, M.J.B.D.
Rajkumar, V.
Sheba, M.
 
Subject sediment
continental slope
tectonic
microorganism
 
Description In the deep subsurface sediments of the Andaman continental slope, in situ methane generation/oxidation could be coupled to the cycling of Mn, as the fluid flow characterized by high methane and Mn could occur in accretionary wedge sediments by diagenetic and tectonic processes. Laboratory studies on Mn cycling by subsurface sediment microbial communities were therefore undertaken 1) to study, further, possible in situ mechanisms of Mn cycling and 2) to examine how Mn redox reactions might be coupled to methane generation/oxidation. Biotic experiments were conducted with uniformly mixed subsamples amended with 100 μM Mn2+ in the presence (G+) and absence (G−) of added glucose (55.5 μM). The corresponding abiotic controls included set-ups poisoned with 15 mM sodium azide. Further, to relate the results of in vitro experiments on Mn cycling, to the methane related processes occurring in the subsurface sediments, pore water concentration of Mn, total cell numbers and the abundance of methanogens, methanotrophs and fermenters were determined. Results of the experiment on Mn cycling showed the immobilization of Mn occurred under oxic conditions and mobilization under suboxic conditions in the absence of added glucose at P ≤ 0.001 with abiotic > biotic. Whereas, in the presence of added glucose, immobilization occurred under both oxic and suboxic conditions at P ≤ 0.001 with biotic > abiotic, oxic > suboxic. The biotic cycling of Mn at 360 mbsf coincided with the total cell numbers (1.53 × 108 cells g−1), increased methane levels (89,100 ppm-v) and the abundance of methanogens (1.0 × 103 MPN g−1). Besides, the distribution of aerobic methanotrophs decreased in abundance with depth. Also, the abundance of fermenters (3.5 × 103 cells g−1) at 626.7 mbsf coincided with the relatively high concentration of Mn (319.1 μM) in sediment pore water. The results indicate that subsurface sediments harbor microorganisms that partake significantly in the cycling of Mn wherein, the availability of organic carbon dictates the direction in which the reactions occur. Besides, aerobic oxidation of methane and Mn has been reported to occur under reducing conditions. Thus, the present findings suggest that Mn redox changes affect the methane oxidation/production rates by serving either as an electron donor and/or an electron acceptor.
 
Date 2015-01-08T08:47:00Z
2015-01-08T08:47:00Z
2014
 
Type Journal Article
 
Identifier Marine and Petroleum Geology, vol.58; 2014; 254-264
no
http://drs.nio.org/drs/handle/2264/4667
 
Language en
 
Relation Mar_Pet_Geol_58_254.jpg
 
Rights An edited version of this paper was published by Elsevier. Copyright [2014] Elsevier
 
Publisher Elsevier