Premium
Methane sources in arctic thermokarst lake sediments on the N orth S lope of A laska
Author(s) -
Matheus Carnevali P. B.,
Rohrssen M.,
Williams M. R.,
Michaud A. B.,
Adams H.,
Berisford D.,
Love G. D.,
Priscu J. C.,
Rassuchine O.,
Hand K. P.,
Murray A. E.
Publication year - 2015
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12124
Subject(s) - thermokarst , methanogenesis , archaea , permafrost , organic matter , arctic , environmental chemistry , sediment , methane , biogeochemistry , chemistry , environmental science , geology , ecology , oceanography , biology , geomorphology , bacteria , paleontology
The permafrost on the N orth S lope of A laska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane ( CH 4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH 4 as a greenhouse gas, the contribution of biogenic CH 4 production in arctic thermokarst lakes in A laska is not currently well understood. To further advance our knowledge of CH 4 dynamics in these lakes, we focused our study on (i) the potential for microbial CH 4 production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH 4 production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in S iqlukaq L ake and two sites in S ukok L ake in late O ctober to early N ovember. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH 4 production experiments, and copy number of a methanogenic pathway‐specific gene ( mcrA ) indicated the existence of different sources of CH 4 in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH 4 production in S iqlukaq at moderate levels, while the very low levels of CH 4 detected in S ukok had a mixed origin, with little to no biological CH 4 production. Furthermore, methanogenic archaea exhibited temperature‐dependent use of in situ substrates for methanogenesis, and the amount of CH 4 produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH 4 from thermokarst lakes on the coastal plain of A laska to the current CH 4 budgets.