Carbon isotopic evidence for microbial control of carbon supply to Orca Basin at the seawater–brine interface

Shah, S. R.; Joye, Samantha B.; Brandes, Jay; McNichol, Ann P.

doi:10.5194/bg-10-3175-2013

Cited by 10 publications

(10 citation statements)

References 42 publications

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“…Strong variations in particle concentration were associated with the changes in temperature and salinity around depths of 2,187 m and 2,225 m. In these specific cases, the camera crossed through thin bands, indicating loss of beam transmission possibly caused by layers of very high particle concentration ( Figures S4 and S5). DOC concentrations were slightly lower but in good agreement with those published by Shah et al (2013).…”

Section: Discussionsupporting

confidence: 89%

“…The mean of measured DOC concentrations in the brine, 241.0 µM ± 65.2 µM (n = 10), results in a total amount of 2.47 × 10 9 moles of DOC stored in the brine, providing a potential source of (refractory) DOC for the abiotic formation of marine snow aggregates as described by (Hansell et al, 2009); in fact, comet-shaped marine snow aggregates several centimeters in length, not seen higher in the water column, were observed just below the transition zone. Some of the DOC comes in with the salt (Joye et al, 2010), but Shah et al (2013) have also suggested microbial conversion (enzymatic hydrolysis) of POC to DOC, as well as physical disaggregation of POC into DOC, based on stable C isotope budgets evaluated across the chemocline.…”

Section: Discussionmentioning

confidence: 99%

“…The deep bottom waters of Orca Basin have been hypersaline for at least the last 7,900 years (Addy and Behrens, 1980;Leventer et al, 1983;Meckler et al, 2008;Shah et al, 2013). Sediments of the basin were reported as anoxic, dark in color, and strongly reducing, transitioning to grey mud below 4.85 m (Addy and Behrens, 1980).…”

Section: Introductionmentioning

confidence: 99%

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Vertical marine snow distribution in the stratified, hypersaline, and anoxic Orca Basin (Gulf of Mexico)

Diercks

Ziervogel

Sibert

et al. 2019

Elementa: Science of the Anthropocene

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We present a complete description of the depth distribution of marine snow in Orca Basin (Gulf of Mexico), from sea surface through the pycnocline to within 10 m of the seafloor. Orca Basin is an intriguing location for studying marine snow because of its unique geological and hydrographic setting: the deepest ~200 m of the basin are filled with anoxic hypersaline brine. A typical deep ocean profile of marine snow distribution was observed from the sea surface to the pycnocline, namely a surface maximum in total particle number and midwater minimum. However, instead of a nepheloid (particle-rich) layer positioned near the seabed, the nepheloid layer in the Orca Basin was positioned atop the brine. Within the brine, the total particle volume increased by a factor of 2–3 while the total particle number decreased, indicating accumulation and aggregation of material in the brine. From these observations we infer increased residence time and retention of material within the brine, which agrees well with laboratory results showing a 2.2–3.5-fold reduction in settling speed of laboratory-generated marine snow below the seawater-brine interface. Similarly, dissolved organic carbon concentration in the brine correlated positively with measured colored dissolved organic matter (r2 = 0.92, n = 15), with both variables following total particle volume inversely through the pycnocline. These data indicate the release of dissolved organic carbon concomitant with loss in total particle volume and increase in particle numbers at the brine-seawater interface, highlighting the importance of the Orca Basin as a carbon sink.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

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Vertical marine snow distribution in the stratified, hypersaline, and anoxic Orca Basin (Gulf of Mexico)

Diercks

Ziervogel

Sibert

et al. 2019

Elementa: Science of the Anthropocene

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“…Porewater concentrations of dissolved organic carbon (DOC) in the Orca Basin sediments reached approx. 5800 μM in north sub-basin sediment and 2200 μM in south sub-basin sediment, and were highly elevated compared to the overlying brine (320 to 350 μM DOC) [7]. In contrast, porewater DOC concentrations of ca.…”

Section: Plos Onementioning

confidence: 86%

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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“…Research groups build devices with various applications of small scale combustor, such as micro burners have been integrated with thermoelectric [5,6] and thermophotovoltaic [7][8][9] for power and energy applications. Other micro combustion applications include micro propulsion [10,11], calorimetry [12], and carbon-isotopic analysis in biogeography [13,14]. As the prospect of small scale combustion is for producing energy at small scales, there are issues related with it.…”

Section: Introductionmentioning

confidence: 99%