Interstitial Water Geochemistry and Clay Mineralogy of the Mississippi Fan and Orca and Pigmy Basins, Deep Sea Drilling Project Leg 96

Ishizuka, T.; Kawahata, Hodaka; Aoki, Saburo

doi:10.2973/dsdp.proc.96.142.1986

Cited by 8 publications

(5 citation statements)

References 5 publications

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“…Over time, the slow microbial degradation of sedimentary organic matter leads to accumulation of a large pool of sedimentary DOC that exceeds the DOC concentrations in the brine and in non-hypersaline sediments by an order of magnitude (Fig 3). The DOC concentrations measured in the north sub-basin MUC core (5800 μM) were consistent with DOC concentrations at greater depth in Orca Basin subsurface sediments at DSDP Site 618, also located in the north sub-basin [92]. At this DSDP site, the lowest DOC value, 63 μg/ml or 5250 μM, is located at 3 mbsf, followed by the highest DOC peak of 18750 μM at 12 mbsf; the remaining values cluster in the range of 80 to 120 μg/ml or 6600 to 10000 μM and are found in subsurface sediments down to 91 mbsf [92].…”

Section: Dissolved Carbon and Ammoniumsupporting

confidence: 72%

Microbial ecology and biogeochemistry of hypersaline sediments in Orca Basin

et al. 2020

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In deep ocean hypersaline basins, the combination of high salinity, unusual ionic composition and anoxic conditions represents significant challenges for microbial life. We used geochemical porewater characterization and DNA sequencing based taxonomic surveys to enable environmental and microbial characterization of anoxic hypersaline sediments and brines in the Orca Basin, the largest brine basin in the Gulf of Mexico. Full-length bacterial 16S rRNA gene clone libraries from hypersaline sediments and the overlying brine were dominated by the uncultured halophilic KB1 lineage, Deltaproteobacteria related to cultured sulfate-reducing halophilic genera, and specific lineages of heterotrophic Bacteroidetes. Archaeal clones were dominated by members of the halophilic methanogen genus Methanohalophilus, and the ammonia-oxidizing Marine Group I (MG-I) within the Thaumarchaeota. Illumina sequencing revealed higher phylum-and subphylum-level complexity, especially in lower-salinity sediments from the Orca Basin slope. Illumina and clone library surveys consistently detected MG-I Thaumarchaeota and halotolerant Deltaproteobacteria in the hypersaline anoxic sediments, but relative abundances of the KB1 lineage differed between the two sequencing methods. The stable isotopic composition of dissolved inorganic carbon and methane in porewater, and sulfate concentrations decreasing downcore indicated methanogenesis and sulfate reduction in the anoxic sediments. While anaerobic microbial processes likely occur at low rates near their maximal salinity thresholds in Orca Basin, long-term accumulation of reaction products leads to high methane concentrations and reducing conditions within the Orca Basin brine and sediments.

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Section: Dissolved Carbon and Ammoniumsupporting

confidence: 72%

Microbial ecology and biogeochemistry of hypersaline sediments in Orca Basin

et al. 2020

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“…Mean organic carbon contents at Sites 689 and 690 were 0.11 and 0.15, respectively, which was comparable to those observed in oligotrophic ocean in the western Pacific (Kawahata, 1999). The high rates of sedimentation and the high concentrations of sedimentary organic carbon lead to extensive sulfate reduction at Sites 473 and 479 (Gieskes et al, 1982) and at Sites 618 and 619 (Ishizuka et al, 1986a).…”

Section: Relationship Between Doc and Total Dissolved Amino Acids In supporting

confidence: 56%

Amino acids in interstitial waters from ODP Sites 689 and 690 on the Maud Rise, Antarctic Ocean.

Kawahata

Ishizuka

2000

Geochem. J.

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Biogenic calcareous and siliceous sediments were drilled at ODP Sites 689 and 690 on the Maud Rise, Antarctic Ocean. We analyzed dissolved combined amino acids (DCAA) and dissolved free amino acids (DFAA) in interstitial waters in order to characterize the amino acids in dissolved organic matter. The DFAA was predominant over the DCAA in interstitial waters at Sites 689 and 690, which contradicted the previous results from interstitial water and seawater studies. The DCAA in the interstitial waters probably originated from calcareous biogenic debris with less amounts of siliceous debris. Although glutamic acid constituted 41% of the total concentration of DCAA, it accounted for only 1% of the total concentration of DFAA due to the adsorption and/or reaction with biogenic carbonate. Ornithine, a nonprotein amino acid, is a decomposed product of arginine and made up 17 mol% of the total DFAA and. The total hydrolyzable amino acids (=DCAA + DFAA) accounted for 5 to 28% of the dissolved organic carbon (DOC) concentration, which implied that high molecular weight organic matter was a major contributor for the DOM (dissolved organic matter) in interstitial waters. Fairly positive correlation between the dissolved manganese and the total DCAA values suggested that the redox condition plays a significant role in controlling the total DCAA content. A small decrease in the sulfate concentration in the interstitial waters from both sites suggested fairly low microbial activity by sulfate-reducing bacteria.

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“…In the light of the discussion given above, this difference is probably related to the fact that Leg 113 sediments contain significantly lower concentrations of sedimentary organic material and that they are deposited at considerably lower rates ( Table 9). The high rates of sedimentation and the high concentrations of sedi mentary organic carbon give rise to more extensive sulfate re duction at Sites 474 and 479 (Gieskes et al, 1982) and at Sites 618 and 619 (Ishizuka et al, 1986a) as compared to the Leg 113 sites. Site 623 is an exception.…”

Section: Discussionmentioning

confidence: 99%

“…and a content of organic carbon of about 1 % (Table 9), the sulfate profile shows no evidence of sulfate re duction. However, the elevated alkalinity levels (Ishizuka et al, 1986a) are indicative of microbial activity. attrib uted the anomalous sulfate profile at Site 623 to unknown pro- (Table 9); open symbols, data from Leg 96 tentatively corrected for the effect of turbidites on the rate of accumula tion.…”

Section: Discussionmentioning

confidence: 99%

The Diagenetic Factors Controlling the Dissolved Organic Carbon (DOC) in Pore Water from Deep Sea Sediments (ODP Leg 113|Weddell Sea)

Abdullah¹

1990

Proceedings of the Ocean Drilling Program

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Dissolved organic carbon (DOC) was determined in pore water extracted from pelagic and hemipelagic sediments re covered during Leg 113. DOC concentration varied between 1.82 and 13.6 mg C/L which is one to two orders of magni tude less than previously reported for hemipelagic sediments. It is argued that this difference is related to differences in the intensity of degradation of organic matter. As a first approximation it is found that in reducing sediments, the level of DOC is proportional to the intensity of sulfate reduction. It is suggested that DOC is formed by different mecha nisms in oxic and reducing environments.

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Interstitial Water Geochemistry and Clay Mineralogy of the Mississippi Fan and Orca and Pigmy Basins, Deep Sea Drilling Project Leg 96

Cited by 8 publications

References 5 publications

Microbial ecology and biogeochemistry of hypersaline sediments in Orca Basin

Microbial ecology and biogeochemistry of hypersaline sediments in Orca Basin

Amino acids in interstitial waters from ODP Sites 689 and 690 on the Maud Rise, Antarctic Ocean.

The Diagenetic Factors Controlling the Dissolved Organic Carbon (DOC) in Pore Water from Deep Sea Sediments (ODP Leg 113|Weddell Sea)

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