@article {Feng2014,
	title = {{Time integrated variation of sources of fluids and seepage dynamics archived in authigenic carbonates from Gulf of Mexico Gas Hydrate Seafloor Observatory}},
	journal = {Chemical Geology},
	volume = {385},
	year = {2014},
	pages = {129{\textendash}139},
	abstract = {Authigenic carbonate rocks recovered from the Gulf of Mexico Gas Hydrate Seafloor Observatory in Mississippi Canyon block 118 (MC118) at approximately 900 m water depth were studied using mineralogical, bulk geochemical, and lipid biomarker analyses. Carbonate rocks occurred as fractured blocks and nodular masses incorporated in carbonate breccias. The carbonates were comprised mainly of high-Mg-calcite and aragonite. The stable carbon isotope composition ($δ$13C) of authigenic carbonate varied from - 29.8{\textperthousand} to - 18.1{\textperthousand} vs. V-PDB, suggesting a complex mixture of various carbon sources, including dissolved marine inorganic carbon (DIC), oil, as well as methane. Oxygen isotopes ($δ$18O) varied from + 3.4{\textperthousand} to + 5.8{\textperthousand}. The observed 18O-enrichment in relation to calculated equilibrium values in the carbonates probably reflects decomposition of gas hydrates. The most abundant lipid biomarkers in the carbonates were isoprenoidal glycerol dibiphytanyl glycerol tetraethers (GDGTs), predominated by GDGT-2 and GDGT-3, which are typically indicators of anaerobic methane oxidizing archaea (ANMEs). Mono- and bicyclic biphytanes (derived after ether cleavage of GDGT-2 and GDGT-3) showed strong 13C-depletion, which is characteristic for ANMEs. Interestingly, large differences between the $δ$13C values of the archaeal diether archaeol and acyclic biphytane on the one hand and monocyclic biphytane on the other hand suggest the presence of archaea other than ANMEs. Archaeol and GDGT-0 (containing two acyclic biphytane moieties) are commonly assigned to various methanogenic archaea. Where methane seepage activity is intermediate or low within acoustic wipeout zones at the MC118 gas hydrate site nowadays, microbial communities must have coped with changing conditions as well as longer-term fluctuations in oil and gas seepage or the temporary cessation of hydrocarbon flux in the past. The change from methane seepage to oil seepage or vice versa in addition to flux variability apparently favors the establishment of complex prokaryotic communities dominated by archaea. In addition to anaerobic oxidation of methane, local production of methane is apparently prominent at the study site based on the occurrence of biomarkers of methanogens in the authigenic carbonate. This finding adds to the ongoing multidisciplinary effort to better constrain the environment at the MC118 observatory site and to determine the locally dominant biogeochemical processes.},
	keywords = {HOV Alvin (Human Occupied Vehicle), ROV Jason (Remotely Operated Vehicle)},
	doi = {10.1016/j.chemgeo.2014.07.020},
	author = {Feng, D and Birgel, D and Peckmann, J and Roberts, H H and Joye, S B and Sassen, R and Liu, X-L and Hinrichs, K -U and Chen, D}
}
@article {Kellermann2012,
	title = {{Symbiont{\textendash}host relationships in chemosynthetic mussels: A comprehensive lipid biomarker study}},
	journal = {Organic Geochemistry},
	volume = {43},
	year = {2012},
	pages = {112{\textendash}124},
	abstract = {Symbiosis with chemosynthetic microorganisms allows invertebrates from hydrothermal vents and cold seeps, such as mussels, snails and tubeworms, to gain nutrition independently of organic input from photosynthetic communities. Lipid biomarkers and their compound specific stable carbon isotopes ($δ$13C) have greatly aided the elucidation of chemosynthetic symbiosis. Due to recent methodological advances in liquid chromatography it is now possible to obtain a more holistic view of lipid biomarkers, including the analysis of intact polar membrane lipids (IPLs) and bacteriohopanepolyols (BHPs). This study provides an extensive examination of polar and apolar lipids in combination with stable carbon isotope analysis of three Bathymodiolus mussels (Bathymodiolus childressi, Bathymodiolus cf. thermophilus, Bathymodiolus brooksi) hosting different types of bacterial symbiont (methane-oxidizing, sulfur-oxidizing and a dual symbiosis with methane- and sulfur-oxidizing symbionts, respectively). We propose that IPLs with C16:1 acyl side chains, and phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylethanolamine (PE) head groups, which were only detected in the gill tissue, can be used as symbiont-characteristic biomarkers. These putative symbiont-specific IPLs provide the opportunity to detect and quantify the methanotrophic and thiotrophic symbionts within the gill tissue. Additional characteristic markers for methanotrophic symbionts were found in B. childressi and B. brooksi, including the BHP derivatives aminotriol and aminotetrol, 4-methyl sterols and diagnostic fatty acids (FAs), such as C16:1${\o}mega$9, C16:1${\o}mega$8, and C18:1${\o}mega$8. In general, the $δ$13C values of FAs, alcohols and BHP-derived hopanols were in accordance with carbon assimilation pathways of the respective methanotrophic or thiotrophic symbionts in all three Bathymodiolus mussels. Differences in BHP distribution as well as $δ$13C values in the two mussels hosting a methanotrophic symbiont may indicate the presence of different methanotrophic symbionts and/or changes in the nutritional status. In all three mussel species the $δ$13C values of lipid biomarkers assigned to the symbionts were similar to those of the hosts, indicating the importance of the bacterial symbionts as the main carbon source for the mussel tissue.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0146-6380},
	doi = {10.1016/j.orggeochem.2011.10.005},
	url = {http://dx.doi.org/10.1016/j.orggeochem.2011.10.005},
	author = {Kellermann, M Y and Schubotz, F and Elvert, M and Lipp, J S and Birgel, D and Prieto-Mollar, X and Dubilier, N and Hinrichs, K -U}
}
@article {Bradley2009a,
	title = {{Structural diversity of diether lipids in carbonate chimneys at the Lost City Hydrothermal Field}},
	journal = {Organic Geochemistry},
	volume = {40},
	number = {12},
	year = {2009},
	pages = {1169{\textendash}1178},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0146-6380},
	doi = {10.1016/j.orggeochem.2009.09.004},
	url = {http://dx.doi.org/10.1016/j.orggeochem.2009.09.004},
	author = {Bradley, A S and Fredricks, H and Hinrichs, K -U and Summons, R E}
}
