Morphological and compositional evidence for biotic precipitation of marine barite

Bertram, Miriam; Cowen, James P.

doi:10.1357/0022240973224292

Cited by 105 publications

(67 citation statements)

References 26 publications

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“…The formation of marine BaSO 4 appears to be critically dependent on the presence of heterotrophic bacteria, which play a key role in the degradation of POC in seawater (particulate organic carbon; e.g. Bertram and Cowen, 1997;González-Muñoz et al, 2003;Ganeshram et al, 2003;González-Muñoz et al, 2012). The majority of these heterotrophic microbes live within 100 m of the base of the euphotic zone where the supply of phytoplankton-derived organic matter is highest (e.g.…”

Section: Origin Of Ba-isotopic Variations In Seawater 421 Organic Mmentioning

confidence: 99%

“…Though seawater is likely the ultimate source of Ba ions to marine BaSO 4 , its precipitation is microbially-mediated (e.g. Bertram and Cowen, 1997), such that intermediate Ba sources may be incorporated during BaSO 4 formation. One likely intermediate Ba source to BaSO 4 formation is organic matter, in addition to Ba sourced from dissolved Ba 2+ in seawater; a continuum between these two end-member sources may also exist (see e.g.…”

Section: Introductionmentioning

confidence: 99%

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Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation

Horner

Kinsley

Nielsen

2015

Earth and Planetary Science Letters

140

247

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Highlights• First full seawater depth profile of co-located [Ba]-δ 138/134 Ba NIST• Origin of Ba-isotopic variations are best explained by barite cycling• Regional circulation strongly influences depth structure of δ 138/134 Ba NIST• Data establish a baseline of Ba-isotopic variability in the marine realm Keywords: barium; isotopic fractionation; barite; seawater; biogeochemistry AbstractThe marine biogeochemical cycle of Ba is thought to be controlled by particulate BaSO 4 (barite) precipitation associated with the microbial oxidation of organic carbon and its subsequent dissolution in the BaSO 4 -undersaturated water column. Despite many of these processes being largely unique to Ba cycling, concentrations of Ba and Si in seawater exhibit a strong linear correlation. The reasons for this correlation are ambiguous, as are the depth ranges corresponding to the most active BaSO 4 cycling and the intermediate sources of Ba to particulate BaSO 4 . Stable isotopic analyses of dissolved Ba in seawater should help address these issues, as Ba-isotopic compositions are predicted to be sensitive to the physical and biogeochemical process that cycle Ba. We report a new methodology for the determination of dissolved Ba-isotopic compositions in seawater and results from a 4, 500 m depth profile in the South Atlantic at 39.99 • S, 0.92 • E that exhibit oceanographically-consistent variation with depth. These data reveal that water masses obtain their [Ba] and Ba-isotopic signatures when at or near the surface, which relates to the cycling of marine BaSO 4 . The shallow origin of these signatures requires that the substantial Ba-isotopic variations in the bathypelagic zone were inherited from when those deep waters were last ventilated. Indeed, the water column below 600 m is well explained by conservative mixing of water masses with distinct [Ba] and Ba-isotopic compositions. This leads us to conclude that large scale oceanic circulation is important for sustaining the similar oceanographic distributions of Ba and Si in the South Atlantic, and possibly elsewhere. These data demonstrate that the processes of organic carbon oxidation, BaSO 4 cycling, and Ba-isotopic fractionation in seawater are closely coupled, such that Ba-isotopic analyses harbor great potential as a tracer of the carbon cycle in the modern and paleo-oceans.

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Section: Origin Of Ba-isotopic Variations In Seawater 421 Organic Mmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation

Horner

Kinsley

Nielsen

2015

Earth and Planetary Science Letters

140

247

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“…Based on dissolved Ba content, temperature, depth and salinity, we calculated the barite saturation indices (Ω) for pure BaSO 4 and for Srsubstituted barites following the procedures described by Monnin et al (1999) and Monnin and Cividini (2006). As previously found (Monnin and Cividini, 2006) excess Ba -barite in the water column is occurring throughout the World Ocean (Bishop, 1988;Dehairs et al, 1980;Bertram and Cowen, 1997;Cardinal et al, 2006) in situations with different plankton community regimes, we will assume as a first order approximation that the Southern Ocean transfer function relating mesopelagic Ba xs content with oxygen consumption applies for this sub-tropical North Pacific environment.…”

Section: Ba Xs Contents and Bacterial Activitymentioning

confidence: 99%

Barium in twilight zone suspended matter as a potential proxy for particulate organic carbon remineralization: Results for the North Pacific

Dehairs

Jacquet

Savoye

et al. 2008

Deep Sea Research Part II: Topical Studies in Oceanography

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This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22°45' N 158°W; Hawaii; studied during June-July 2004) and the mesotrophic Subarctic Pacific K2 site (47°N, 161°W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Ba xs ) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general Ba xs contents were significantly larger at K2 than at ALOHA. At ALOHA the Ba xs profiles

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“…Several explanations have been proposed for the nutrient-like behaviour of Ba in seawater, though there is now considerable laboratory (Ganeshram et al, 2003;González-Munoz et al, 2003), field (Dehairs et al, 1980;Collier and Edmond, 1984), morphological (Bertram and Cowen, 1997), geochemical (Griffith and Paytan, 2012) and thermodynamic (Monnin et al, 1999) evidence to suggest that the formation of discrete, micron-sized barite (BaSO 4 ) crystals in the water column is a biological or biologically-mediated process, and that BaSO 4 is the major vector of particulate Ba in the modern water column. However, these observations do not address the mechanisms behind the similar depth profiles of [Ba] and Si(OH) 4 , which have been proposed to relate to the similar remineralisation depths of their respective carrier phases (BaSO 4 and opal, respectively; e.g.…”

Section: Introductionmentioning

confidence: 99%

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Bates

Hendry

Pryer

et al. 2017

Geochimica et Cosmochimica Acta

134

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We diagnose the relative influences of local-scale biogeochemical cycling and regional-scale ocean circulation on Atlantic barium cycling by analysing four new depth profiles of dissolved Ba concentrations and isotope compositions from the South and tropical North Atlantic. These new profiles exhibit systematic vertical, zonal and meridional variations that reflect the influence of both local-scale barite cycling and large-scale ocean circulation. Epipelagic decoupling of dissolved Ba and Si reported previously in the tropics is also found to be associated with significant Ba isotope heterogeneity. As such, we contend that this decoupling originates from the depth segregation of opal and barite formation but is exacerbated by weak vertical mixing. Zonal influence from isotopically-'heavy' water masses in the western North Atlantic evidence the advective inflow of Ba-depleted Upper Labrador Sea Water, which is not seen in the eastern basin or the South Atlantic. Meridional variations in Atlantic Ba isotope systematics below 2000 m appear entirely controlled by conservative mixing. Using an inverse isotopic mixing model, we calculate the Ba isotope composition of the Ba-poor northern end-member as +0.45 ‰ and the Ba-rich southern end-member +0.26 ‰, relative to NIST SRM 3104a. The near-conservative behaviour of Ba below 2000 m indicates that Ba isotopes can serve as an independent tracer of the provenance of northern-versus southern-sourced water masses in the deep Atlantic Ocean. This finding may prove useful in palaeoceanographic studies, should appropriate sedimentary archives be identified, and offers new insights into the processes that cycle Ba in seawater.

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Morphological and compositional evidence for biotic precipitation of marine barite

Cited by 105 publications

References 26 publications

Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation

Barium-isotopic fractionation in seawater mediated by barite cycling and oceanic circulation

Barium in twilight zone suspended matter as a potential proxy for particulate organic carbon remineralization: Results for the North Pacific

Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

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