Interstitial fluid chemistry of sediments underlying the North Atlantic gyre and the influence of subsurface fluid flow

Ziebis, Wiebke; McManus, James; Ferdelman, Timothy G.; Schmidt-Schierhorn, Friederike; Bach, Wolfgang; Muratli, Jesse M; Edwards, Katrina J.; Villinger, Heinrich

doi:10.1016/j.epsl.2012.01.018

Cited by 70 publications

(100 citation statements)

References 46 publications

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“…In contrast to well-studied ocean margin sediments, oxygen (O 2 ) and nitrate (NO − 3 ), two powerful oxidants of organic carbon, penetrate deeply into the sediment underlying oligotrophic ocean waters (D'Hondt et al, , 2015Murray and Grundmanis, 1980;Rutgers van der Loeff et al, 1990;Sachs et al, 2009;Røy et al, 2012;Fischer et al, 2009). Furthermore, in the sediments overlying relatively young and permeably ocean crust, O 2 and NO − 3 are also supplied via upward diffusion from oxic and nitrate-replete fluids flowing through basaltic basement as has been shown for the North Pond site, which is located on the western flank of the Mid-Atlantic Ridge (Orcutt et al, 2013;Ziebis et al, 2012). At North Pond, where the sediment cover is thin (< ∼ 25 m), O 2 penetrates the entire sediment column; where sediment thickness is elevated, conditions become anoxic at mid-depths.…”

Section: Introductionmentioning

confidence: 99%

“…2) ) is also supplied via diffusion from the underlying basaltic crustal aquifer (Fig. 2) (Orcutt et al, 2013;Ziebis et al, 2012). Although not measured during this work, sediment organic carbon and nitrogen content was measured on several of the piston cores collected during the site survey, averaging 0.15 and 0.02 %, respectively (Ziebis et al, 2012).…”

Section: Previous Measurements Of Dissolved Oxygen and Organic Mattermentioning

confidence: 99%

“…While a majority of seafloor subsurface biosphere research has focused on aspects of sedimentary carbon, sulfur, and iron cycles, the potential role of N in supporting subsurface microbial activity has been largely unexplored. Despite exceedingly oligotrophic conditions, life persists and evidence for active heterotrophic and autotrophic microbial communities in North Pond sediments is mounting (Ziebis et al, 2012;Picard and Ferdelman, 2011;Orcutt et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Nitrogen cycling in the deep sedimentary biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

et al. 2015

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Abstract. Nitrogen (N) is a key component of fundamental biomolecules. Hence, its cycling and availability are central factors governing the extent of ecosystems across the Earth. In the organic-lean sediment porewaters underlying the oligotrophic ocean, where low levels of microbial activity persist despite limited organic matter delivery from overlying water, the extent and modes of nitrogen transformations have not been widely investigated. Here we use the N and oxygen (O) isotopic composition of porewater nitrate (NO − 3 ) from a site in the oligotrophic North Atlantic (Integrated Ocean Drilling Program -IODP) to determine the extent and magnitude of microbial nitrate production (via nitrification) and consumption (via denitrification). We find that NO − 3 accumulates far above bottom seawater concentrations (∼ 21 µM) throughout the sediment column (up to ∼ 50 µM) down to the oceanic basement as deep as 90 m b.s.f. (below sea floor), reflecting the predominance of aerobic nitrification/remineralization within the deep marine sediments. Large changes in the δ 15 N and δ 18 O of nitrate, however, reveal variable influence of nitrate respiration across the three sites. We use an inverse porewater diffusion-reaction model, constrained by the N and O isotope systematics of nitrification and denitrification and the porewater NO − 3 isotopic composition, to estimate rates of nitrification and denitrification throughout the sediment column. Results indicate variability of reaction rates across and within the three boreholes that are generally consistent with the differential distribution of dissolved oxygen at this site, though not necessarily with the canonical view of how redox thresholds separate nitrate regeneration from dissimilative consumption spatially. That is, we provide stable isotopic evidence for expanded zones of co-occurring nitrification and denitrification. The isotope biogeochemical modeling also yielded estimates for the δ 15 N and δ 18 O of newly produced nitrate (δ 15 N NTR (NTR, referring to nitrification) and δ 18 O NTR ), as well as the isotope effect for denitrification ( 15 ε DNF ) (DNF, referring to denitrification), parameters with high relevance to global ocean models of N cycling. Estimated values of δ 15 N NTR were generally lower than previously reported δ 15 N values for sinking particulate organic nitrogen in this region. We suggest that these values may be, in part, related to sedimentary N 2 fixation and remineralization of the newly fixed organic N. Values of δ 18 O NTR generally ranged between −2.8 and 0.0 ‰, consistent with recent estimates based on lab cultures of nitrifying bacteria. Notably, some δ 18 O NTR values were elevated, suggesting incorporation of 18 O-enriched dissolved oxygen during nitrification, and possibly indicating a tight coupling of NH + 4 and NO − 2 oxidation in this metabolically sluggish environment. Our findings indicate that the production of organic matter by in situ autotrophy (e.g., nitrification, nitrogen fixation) supplies a large fraction of the...

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Section: Introductionmentioning

confidence: 99%

Section: Previous Measurements Of Dissolved Oxygen and Organic Mattermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nitrogen cycling in the deep sedimentary biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

et al. 2015

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“…old western flank of the Mid-Atlantic Ridge at 23°N were sampled during the Expedition 336 site survey cruise with the German R/V Maria S. Merian in 2009 (MSM 11/1). Sediment cores (12 cm diameter) were successfully retrieved at six locations within the North Pond basin between 4040 and 4480 meters below sea level using gravity corers (Ziebis et al, 2012). These cores extended to 8 mbsf.…”

Section: Methodsmentioning

confidence: 99%

“…old western flank of the Mid-Atlantic Ridge at 23°N have been shown to contain molecular oxygen downhole to >8 m sediment depth. Aerobic respiration likely dominates organic carbon oxidation (Ziebis et al, 2012). During a site survey cruise prior to Integrated Ocean Drilling Program (IODP) Expedition 336 to North Pond, sediment cores were collected to 8 meters below seafloor (mbsf).…”

Section: Introductionmentioning

confidence: 99%

Data report: total cell counts and qPCR abundance of Archaea and Bacteria in shallow subsurface marine sediments of North Pond: gravity cores collected during site survey cruise prior to IODP Expedition 336

Breuker¹

2013

Proceedings of the IODP

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Late Pleistocene stratigraphy of IODP Site U1396 and compiled chronology offshore of south and south west Montserrat, Lesser Antilles

Wall-Palmer

Coussens

Talling

et al. 2014

Geochem Geophys Geosyst

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Marine sediments around volcanic islands contain an archive of volcaniclastic deposits, which can be used to reconstruct the volcanic history of an area. Such records hold many advantages over often incomplete terrestrial data sets. This includes the potential for precise and continuous dating of intervening sediment packages, which allow a correlatable and temporally constrained stratigraphic framework to be constructed across multiple marine sediment cores. Here we discuss a marine record of eruptive and masswasting events spanning 250 ka offshore of Montserrat, using new data from IODP Expedition 340, as well as previously collected cores. By using a combination of high-resolution oxygen isotope stratigraphy, AMS radiocarbon dating, biostratigraphy of foraminifera and calcareous nannofossils, and clast componentry, we identify five major events at Soufriere Hills volcano since 250 ka. Lateral correlations of these events across sediment cores collected offshore of the south and south west of Montserrat have improved our understanding of the timing, extent and associations between events in this area. Correlations reveal that powerful and potentially erosive density-currents traveled at least 33 km offshore and demonstrate that marine deposits, produced by eruption-fed and mass-wasting events on volcanic islands, are heterogeneous in their spatial distribution. Thus, multiple drilling/coring sites are needed to reconstruct the full chronostratigraphy of volcanic islands. This multidisciplinary study will be vital to interpreting the chaotic records of 3000Geochemistry, Geophysics, Geosystems PUBLICATIONS submarine landslides at other sites drilled during Expedition 340 and provides a framework that can be applied to the stratigraphic analysis of sediments surrounding other volcanic islands.

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Interstitial fluid chemistry of sediments underlying the North Atlantic gyre and the influence of subsurface fluid flow

Cited by 70 publications

References 46 publications

Nitrogen cycling in the deep sedimentary biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

Nitrogen cycling in the deep sedimentary biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

Data report: total cell counts and qPCR abundance of Archaea and Bacteria in shallow subsurface marine sediments of North Pond: gravity cores collected during site survey cruise prior to IODP Expedition 336

Late Pleistocene stratigraphy of IODP Site U1396 and compiled chronology offshore of south and south west Montserrat, Lesser Antilles

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