Publication Date:
2024-01-09
Description:
Sediment samples ranging from 0.05 to 278 m below sea floor (mbsf) at a Northwest Pacific deep-water (5564 mbsl) site (ODP Leg 191, Site 1179) were analyzed for phospholipid fatty acids (PLFAs). Total PLFA concentrations decreased by a factor of three over the first meter of sediment and then decreased at a slower rate to approximately 30 mbsf. The sharp decrease over the first meter corresponds to the depth of nitrate and Mn(IV) reduction as indicated by pore water chemistry. PLFA-based cell numbers at site 1179 had a similar depth profile as that for Acridine orange direct cell counts previously made on ODP site 1149 sediments which have a similar water depth and lithology. The mole percentage of straight chain saturated PLFAs increases with depth, with a large shift between the 0.95 and 3.95 mbsf samples. PLFA stable carbon isotope ratios were determined for sediments from 0.05 to 4.53 mbsf and showed a general trend toward more depleted d13C values with depth. Both of these observations may indicate a shift in the bacterial community with depth across the different redox zones inferred from pore water chemistry data. The PLFA 10me16:0, which has been attributed to the bacterial genera Desulfobacter in many marine sediments, showed the greatest isotopic depletion, decreasing from -20 to -35 per mil over the first meter of sediment. Pore water chemistry suggested that sulfate reduction was absent or minimal over this same sediment interval. However, 10me16:0 has been shown to be produced by recently discovered anaerobic ammonium oxidizing (anammox) bacteria which are known chemoautotrophs. The increasing depletion in d13C of 10me16:0 with the unusually lower concentration of ammonium and linear decrease of nitrate concentration is consistent with a scenario of anammox bacteria mediating the oxidation of ammonium via nitrite, an intermediate of nitrate reduction.
Keywords:
10-methyl-Hexadecanoic acid of total fatty acids (IUPAC: 10-methylhexadecanoic acid); 10-methyl-Octadecanoic acid of total fatty acids; 10-methyl-Pentadecanoic acid of total fatty acids; 10-methyl-Tetradecanoic acid of total fatty acids; 11-methyloctadec-12-enoic acid of total fatty acids; 12-methyl-Tetradecanoic acid of total fatty acids (IUPAC: 12-methyltetradecanoic acid); 14-methyl-Hexadecanoic acid of total fatty acids (IUPAC: 14-methylhexadecanoic acid); 191-1179; Cells; cis-9-Hexadecenoic acid of total fatty acids (IUPAC: (9Z)-hexadec-9-enoic acid); COMPCORE; Composite Core; cyclo-Nonadecanoic acid of total fatty acids (IUPAC: Methyleneoctadecanoic acid); Cyclopropane fatty acid of total fatty acids (IUPAC: Methylenehexadecanoic acid); DEPTH, sediment/rock; Docosanoic acid of total fatty acids; Heneicosanoic acid of total fatty acids; Heptadecanoic acid of total fatty acids; Heptadecenoic acid/15-methyl-heptadecanoic acid ratio; Heptadecenoic acid of total fatty acids; Hexacosanoic acid of total fatty acids; Hexadecanoic acid of total fatty acids; Icosanoic acid of total fatty acids; iso-Heptadecanoic acid of total fatty acids (IUPAC: 15-methylhexadecanoic acid); iso-Hexadecanoic acid of total fatty acids (IUPAC: 14-methylpentadecanoic acid); iso-Octadecanoic acid of total fatty acids; iso-Pentadecanoic acid of total fatty acids (IUPAC: 13-methyltetradecanoic acid); Joides Resolution; Leg191; Methyleicosanoic acid of total fatty acids; Methylnonadecanoic acid of total fatty acids; Nonadecanoic acid of total fatty acids; North Pacific Ocean; Ocean Drilling Program; Octadecanoic acid of total fatty acids; ODP; Pentadecanoic acid of total fatty acids; Phospholipid fatty acids; Saturated fatty acids of total fatty acids; Tetracosanoic acid of total fatty acids; Tetradecanoic acid of total fatty acids; Total branched fatty acids of total fatty acids; Tricosanoic acid of total fatty acids; Unsaturated fatty acids/cyclic fatty acids ratio
Type:
Dataset
Format:
text/tab-separated-values, 370 data points
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