The marine biogeochemistry of molybdenum

Tuit, Caroline B.

doi:10.1575/1912/2431

Cited by 22 publications

(15 citation statements)

References 43 publications

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“…The normalized concentration to S = 35 was 107 ± 7 nmol/ kg (n = 168). These values are in good agreement with literature data (Collier, 1985;Sohrin et al, 1987;Tuit and Ravizza, 2003;Firdaus et al, 2008 showed uniform profiles at the other six stations as well as the above three stations. There are no significant inter ocean variations.…”

Section: Data For δsupporting

confidence: 92%

“…Another possibility is that small and real deviations from conservative behavior actually exist for Mo. Non-conservative signatures have actually been observed for dissolved Mo concentrations in estuarine and coastal waters (Dellwig et al, 2007;Rahaman et al, 2010) and in the eastern tropical Pacific (Tuit and Ravizza, 2003). The non-conservative signatures also reported for δ 98/ 95 Mo in the low salinity zone of an estuary (Pearce et al, 2010a).…”

Section: Homogeneity Of Mo Isotopes In the Modern Oxic Oceanmentioning

confidence: 91%

“…Mo is present in oxic seawater predominantly as dissolved MoO 4 2- (Bertine, 1972). Mo has a concentration as high as 107 nmol/kg (normalized to a salinity (S) of 35) and is distributed uniformly in the modern oxic ocean with a residence time of ~800 ky (Collier, 1985;Sohrin et al, 1987;Tuit and Ravizza, 2003;Firdaus et al, 2008). Because of this uniformity, it has been implicitly assumed that Mo isotopes are homogeneously distributed in the ocean, with δ 98/95 Mo of ~2.3‰ on the basis of measure- Fig.…”

Section: Introductionmentioning

confidence: 99%

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The molybdenum isotopic composition of the modern ocean

et al. 2012

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Wang et al., 2011 (1) and is converted to δ 97/95 Mo by multiplying 0.67 when the system follows mass-dependent fractionation. Though no commonly-used Mo isotopic standard currently exists (see later), the standards used by different laboratories do appear to be isotopically similar at the level of 0.1-0.2‰. Continental rock samples, such as granite, basalt, and clastic sediments, have δ 98/95 Mo of ~0.1‰ Siebert et al., 2003). Ferromanganese oxides, which scavenge Mo from seawater in oxic conditions, have a light isotopic signature (δ 98/95 Mo = -1.0 to -0.5‰; Siebert et al., 2003), whereas sediments formed in euxinic conditions (aqueous H 2 S concentrations higher than ~11 µM, the action point pro-The molybdenum isotopic composition of the modern ocean (Received September 13, 2011; Accepted January 5, 2012) Natural variations in the isotopic composition of molybdenum (Mo) are showing increasing potential as a tool in geochemistry. Although the ocean is an important reservoir of Mo, data on the isotopic composition of Mo in seawater are scarce. We have recently developed a new method for the precise determination of Mo isotope ratios on the basis of preconcentration using a chelating resin and measurement by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), which allows us to measure every stable Mo isotope . In this study, 172 seawater samples obtained from 9 stations in the Pacific, Atlantic, and Southern Oceans were analyzed, giving global coverage and the first full depth-profiles. The average isotope composition in δ Three-isotope plots for the Mo isotopes were fitted with straight lines whose slopes agreed with theoretical values for mass-dependent isotope fractionation. These results demonstrate that Mo isotopes are both uniformly distributed and follow a mass-dependent fractionation law in the modern oxic ocean. In addition, Mo isotopic analysis revealed that δ 98/95 Mo of the standard used in this study was 0.117 ± 0.009‰ lighter than the Mo standard that was used by Archer and Vance (2008). A common Mo standard is urgently required for the precise comparison of Mo isotopic compositions measured in different laboratories. On the other hand, our results strongly support the possibility of seawater as an international reference material for Mo isotopic composition.

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Section: Data For δsupporting

confidence: 92%

Section: Homogeneity Of Mo Isotopes In the Modern Oxic Oceanmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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The molybdenum isotopic composition of the modern ocean

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“…Filter digestion and metal analyses are described in detail in Tuit (2003). Briefly, metal samples were treated by refluxing with 950 l HNO 3 and 50 l HF at 120ЊC for 4 h in a closed Teflon vial to dissolve particulate matter and cells (Cullen and Sherrell 1999).…”

mentioning

confidence: 99%

Diel variation of molybdenum and iron in marine diazotrophic cyanobacteria

Tuit

Waterbury

Ravizza

2004

Limnology & Oceanography

137

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Measurements of Mo : C and Fe : C ratios in cultured cells of two N 2 -fixing cyanobacteria, Crocosphaera watsonii strain WH8501 and Trichodesmium erythraeum strain IMS101, agree with estimated metal : carbon ratios based on growth rate and the metal use efficiency of the nitrogenase enzyme. Crocosphaera, a single-celled nocturnal N 2 fixer, showed two-to eightfold increases in Mo and Fe cellular concentrations in response to nitrogen fixation activity. Mo required for N 2 assimilation can account for almost the entire Mo pool measured in the cells, implying that Crocosphaera synthesizes its entire nitrogenase pool de novo each night. In contrast, cultures of Trichodesmium, a filamentous, diurnal N 2 -fixing cyanobacterium, did not show diel variations in Mo or Fe carbon ratios or in cellular metal concentrations. Trichodesmium appears to maintain an internal pool of Mo. In Trichodesmium cultures, Mo concentrations were up to 30% higher than needed to support measured N 2 fixation. Trichodesmium colonies collected from the field had Mo : C ratios 10-fold larger than those measured in culture, far in excess of what is needed to fix N 2 at rates normally measured in the field, despite equivalent Fe : C ratios (66 Ϯ 39 [field samples] and 87 Ϯ 64 [cultures] mol mol Ϫ1 ). The average Fe : C ratio measured in N 2 -fixing Crocosphaera (16 Ϯ 11 mol mol Ϫ1 ) was equivalent to theoretical estimates of Fe demand based on nitrogenase requirements (13 Ϯ 5 mol mol Ϫ1 ). These results demonstrate the extremely efficient use of Fe by these organisms and provide support for the use of theoretical estimates of Fe : C ratios to calculate biological Fe demand for N 2 fixation.Nitrogen fixation, the conversion of N 2 gas into bioavailable forms, is an important source of nitrogen for primary production in the oligotrophic ocean (Capone et al. 1997;Karl et al. 1997). Nitrogen fixation is catalyzed by the nitrogenase complex, a metal-rich enzyme containing 2 mol molybdenum (Mo) and 38-50 mol iron (Fe) mol Ϫ1 complex. Recent studies have focused on Fe as a potentially limiting nutrient for both photoautotrophic growth and N 2 fixation in the marine environment (Sunda and Huntsman 1995;Berman-Frank et al. 2001a;Kustka et al. 2002). Although there is an ongoing debate whether the high levels of sulfate (SO ) in seawater can competitively inhibit molybdate 2Ϫ 4 1 To whom correspondence should be addressed. Present address: Department of Geosciences, Princeton University, Princeton, New Jersey 08544 (ctuit@princeton.edu).2 Present address: Department of Geology & Geophysics, SOEST, University of Hawaii, Manoa, 1680 East-West Road, Honolulu, Hawaii 96822. AcknowledgmentsWe are grateful to Eric Webb for his input throughout this study and for his analysis of the Trichodesmium genome for the putative Mo transporter. We thank James Howard for discussions about nitrogenase and acetylene reduction methods. We also thank Rob Sherrell, Dan McCorkle, and two anonymous reviewers for their comments on the early versions of this manuscript. M...

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“…Coastal Mo distribution is also influenced by freshwater-seawater mixing (Dalai et al, 2005). Some studies, however, have indicated non-conservative behavior in coastal waters, both at the sediment water interface (SWI; Crusius et al, 1996;Adelson et al, 2001;Chaillou et al, 2002;ElbazPoulichet et al, 2005) and in the water column (Tuit and Ravizza, 2003;Dellwig et al, 2007). When phytoplankton is decomposed by bacteria, organic compounds are released and Mo-enriched aggregates are subsequently formed which settle on the sediment water interface where they are rapidly decomposed by microbial activity, contributing to a substantial release of Mo in bottom waters (Dellwig et al, 2007).…”

Section: Mo/camentioning

confidence: 99%

The Application of Long-Lived Bivalve Sclerochronology in Environmental Baseline Monitoring

Steinhardt¹,

Butler

Carroll

et al. 2016

Front. Mar. Sci.

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Assessments of the impact of construction, operation, and removal of large infrastructures and other human activities on the marine environment are limited because they do not fully quantify the background baseline conditions and relevant scales of natural variability. Baselines as defined in Environmental Impact Assessments typically reflect the status of the environment and its variability drawn from published literature and augmented with some short term site specific characterization. Consequently, it can be difficult to determine whether a change in the environment subsequent to industrial activity is within or outside the range of natural background variability representative of an area over decades or centuries. An innovative approach that shows some promise in overcoming the limitations of traditional baseline monitoring methodology involves the analysis of shell material (sclerochronology) from molluscs living upon or within the seabed in potentially affected areas. Bivalves especially can be effective biomonitors of their environment over a wide range of spatial and temporal scales. A rapidly expanding body of research has established that numerous characteristics of the environment can be reflected in morphological and geochemical properties of the carbonate material in bivalve shells, as well as in functional responses such as growth rates. In addition, the annual banding pattern in shells can provide an absolute chronometer of environmental variability and/or industrial effects. Further, some species of very long-lived bivalves can be crossdated back in time, like trees, by comparing these annual banding patterns in their shells. It is therefore feasible to develop extended timeseries of certain marine environmental variables that can provide important insights into long temporal scales of baseline variability. We review recent innovative work on the shell structure, morphology, and geochemistry of bivalves and conclude that they have substantial potential for use as monitors of environmental variability and the effects of pollutants and disturbance.

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The marine biogeochemistry of molybdenum

Cited by 22 publications

References 43 publications

The molybdenum isotopic composition of the modern ocean

The molybdenum isotopic composition of the modern ocean

Diel variation of molybdenum and iron in marine diazotrophic cyanobacteria

The Application of Long-Lived Bivalve Sclerochronology in Environmental Baseline Monitoring

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