Archaeal lipids in Mediterranean cold seeps: molecular proxies for anaerobic methane oxidation

Abstract

Abstract-We investigated the distributions and ␦ 13 C values of biomarkers for Archaea associated with anaerobic methane oxidation in disparate settings throughout two Eastern Mediterranean mud dome fields. All major classes of archaeal lipids are present in the studied sediments, including isoprenoid glycerol diethers, isoprenoid glycerol dialkyl glycerol tetraethers, and irregular isoprenoid hydrocarbons. Of the compounds present, many, including a novel glycerol tetraether and sn-3-hydroxyarchaeol, have not been previously reported for settings in which methane oxidation is presumed to occur. Archaeal lipids are depleted in 13 C, indicating that the Archaea from which they derive are either directly or indirectly involved with methane consumption. The most widespread archaeal lipids are archaeol, PMI, and glycerol tetraethers, and these compounds are present at all active sites. However, archaeal lipid abundances and distributions are highly variable; ratios of crocetane, PMI, and hydroxyarchaeol relative to archaeol vary from 0 to 6.5, from 0 to 2, and from 0 to 1, respectively. These results suggest that archaeal communities differ amongst the sites examined. In addition, carbon isotopic variability amongst archaeal biomarkers in a given mud breccia can be as large as 24 ‰, suggesting that even at single sites multiple archaeal species perform or are supported by anaerobic methane oxidation.

Intact polar and core glycerol dibiphytanyl glycerol tetraether lipids in the Arabian Sea oxygen minimum zone. Part II: Selective preservation and degradation in sediments and consequences for the TEX86

“…Indeed, changes in CL distributions reflecting input of sedimentary methane-oxidizing Euryarchaeota have been observed in other sulfate-methane transition zones (e.g. Pancost et al, 2001;Weijers et al, 2011). These zones likely contain highly active archaeal communities which are productive over prolonged time periods, in an anoxic environment and thus slower degradation kinetics.…”

“…GDGTs are preserved well in the sedimentary record and can thus be used as biomarkers for this group of Archaea (e.g. Kuypers et al, 2001;Pancost et al, 2001;Ingalls et al, 2006;Coolen et al, 2007). Schouten et al (2002) found a correlation between sea surface temperature (SST) and the distribution of four specific GDGTs present in sediment core tops (GDGT-1, -2, -3 and -4 0 , Fig.…”

Substrate potential of Eemian to Holocene permafrost organic matter for future microbial greenhouse gas production

“…However, the core lipids are very stable over geological time scales (Pease et al, 1998;Schouten et al, 2013) and can be found in many different habitats (Bischoff et al, 2013;Schouten et al, 2013). Past bacterial (branched GDGTs (Weijers et al, 2006)) and archaeal (isoprenoid-GDGTs (Koga et al, 1993;Pancost et al, 2001)) markers provide information on the abundance and most likely also on the activity of microbial communities in the geological past. Periods of increased OM accumulation 20 and increased past microbial activity can be observed in the Yedoma deposits (MIS 3 and 4).…”

Glycerol ether biomarkers and their carbon isotopic compositions in a cold seep carbonate chimney from the Shenhu area, northern South China Sea

“…Ar is one of the most common core ether lipids in archaea and is especially prominent in thermophiles, halophiles, and methanogens [46]. Ar is universally present in anaerobic sediments at cold seeps associated with gas hydrates, modern methane seep systems, and methane-rich mud volcanoes [8,[46][47][48]. In AOM environments, the incorporation of methane derived from carbon into these lipids is indicated by their very low δ 13 C values.…”

“…Because archaeal anaerobic methanotrophy results in highly 13 C-depleted lipids, monocyclic MDGD is derived from methanotrophic archaea [54]. This type of archaea biosynthesize structurally related GDGTs containing biphytane chains with one or two cyclopentane rings [48,56,57]. The thermophilic methanogen Methanococcus jannaschii is the only archaeon known to contain the macrocyclic diether as its core membrane lipid [58].…”