Concentration and natural stable isotope profiles of nitrogen species in theBlack Sea

Fuchsman, Clara A.; Murray, James; Konovalov, Sergey

doi:10.1016/j.marchem.2008.04.009

Cited by 79 publications

(107 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Kasting and Siefert, 2001); b. the minimum rate applies at low atmospheric CH 4 levels and before the onset of widespread biological methanogenesis; c. assumes regeneration of FeNi alloy catalysts at high rates equivalent to water flux through ocean crust, but tectonic regeneration is likely ratelimiting; d. produced NH 3 may be rapidly destroyed by photolysis (e.g. Kuhn and Atreya, 1979 Habicht et al (2002), nitrogen levels based on concentrations in the Black Sea (Brewer and Murray, 1973;Fuchsman and Murray, 2008). For nitrogen, solid lines = NH 4 + /NH 3 -NO 2 --NO 3 -system relevant for nitrification, dashed lines = NH 4 + /NH 3 -N 2 -NO 3 -system relevant for denitrification.…”

Section: Discussionmentioning

confidence: 99%

“…Otherwise it would not be detectable in the δ 15 N record (Section 3.1). For illustration, the maximum nitrate concentration in the Black Sea, where nitrate is too scarce to leave an isotopic signature (Fulton et al, 2012), is roughly 3.5μM (Fuchsman and Murray, 2008), whereas the open ocean has concentrations up to around 35μM with nitrate being the major nitrogen source (Sverdrup et al, 1942). The threshold may lie somewhere between these two bounds, but it is probably variable, depending on productivity and the relative abundances of prokaryotes and eukaryotes.…”

Section: Nitrogen As a Redox Proxymentioning

confidence: 99%

“…The NH 4 + that is released during organic matter degradation can accumulate in anoxic waters such as the modern Black Sea (Fuchsman and Murray, 2008) and serve as a nitrogen source. Non-quantitative NH 4 + assimilation imparts a fractionation of up to -27‰ when [NH 4 + ] > 20 μM, but the fractionation decreases to -4‰ at lower concentrations (Hoch et al, 1992;Pennock et al, 1996;Waser et al, 1998).…”

Section: A Primer On Nitrogen Isotopes In Geological Samplesmentioning

confidence: 99%

“…organisms that assimilated a small proportion of the available NH 4 + pool) and a complementary heavy reservoir in sediments elsewhere, representing uptake of the residual heavy dissolved NH 4 + . There is no known modern example of this scenario, because in the case of the Black Sea, the dissolved NH 4 + does not reach far into the photic zone where most productivity occurs (Fuchsman and Murray, 2008). However, this mechanism has M A N U S C R I P T ACCEPTED MANUSCRIPT 7 been invoked for Cretaceous anoxic events (Higgins et al, 2012) and the late Paleoproterozoic (Papineau et al, 2009).…”

Section: A Primer On Nitrogen Isotopes In Geological Samplesmentioning

confidence: 99%

See 3 more Smart Citations

The evolution of Earth's biogeochemical nitrogen cycle

Stüeken

Kipp

Koehler

et al. 2016

Earth-Science Reviews

312

287

View full text Add to dashboard Cite

Nitrogen is an essential nutrient for all life on Earth and it acts as a major control on biological productivity in the modern ocean. Accurate reconstructions of the evolution of life over the course of the last four billion years therefore demand a better understanding of nitrogen bioavailability and speciation through time. The biogeochemical nitrogen cycle has evidently been closely tied to the redox state of the ocean and atmosphere. Multiple lines of evidence indicate that the Earth"s surface has passed in a non-linear fashion from an anoxic state in the Hadean to an oxic state in the later Phanerozoic. It is therefore likely that the nitrogen cycle has changed markedly over time, with potentially severe implications for the productivity and evolution of the biosphere. Here we compile nitrogen isotope data from the literature and review our current understanding of the evolution of the nitrogen cycle, with particular emphasis on the Precambrian. Combined with recent work on redox conditions, trace metal availability, sulfur and iron cycling on the early Earth, we then use the nitrogen isotope record as a platform to test existing and new hypotheses about biogeochemical pathways that may have controlled nitrogen availability through time. Among other things, we conclude that (a) abiotic nitrogen sources were likely insufficient to sustain a large biosphere, thus favoring an early origin of biological N 2 fixation, (b) evidence of nitrate in the Neoarchean and Paleoproterozoic confirm current views of increasing surface oxygen levels at those times, (c) abundant ferrous iron and sulfide in the midPrecambrian ocean may have affected the speciation and size of the fixed nitrogen reservoir, and (d) nitrate availability alone was not a major driver of eukaryotic evolution.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Nitrogen As a Redox Proxymentioning

confidence: 99%

Section: A Primer On Nitrogen Isotopes In Geological Samplesmentioning

confidence: 99%

Section: A Primer On Nitrogen Isotopes In Geological Samplesmentioning

confidence: 99%

See 2 more Smart Citations

The evolution of Earth's biogeochemical nitrogen cycle

Stüeken

Kipp

Koehler

et al. 2016

Earth-Science Reviews

312

287

View full text Add to dashboard Cite

show abstract

“…DeVries et al (2012) used N xs 2 measurements coupled with a global circulation model to estimate oceanic water-column N-loss rates. In anoxic waters of the Black Sea, interannual variations in N xs 2 were attributed to changes in the downward flux of organic matter from phytoplankton blooms (Fuchsman et al, 2008). Despite these efforts many questions remain regarding the role of organic matter flux for fueling water column N-loss (Brettar and Rheinheimer, 1992;Liu and Kaplan, 1984;Ward et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Biogenic nitrogen gas production at the oxic–anoxic interface in the Cariaco Basin, Venezuela

et al. 2013

View full text Add to dashboard Cite

Abstract. Excess nitrogen gas (N xs2 ) was measured in samples collected at six locations in the eastern and western sub-basins of the Cariaco Basin, Venezuela, in September 2008 (non-upwelling conditions) and March 2009 (upwelling conditions). During both sampling periods, N xs 2 concentrations were below detection in surface waters, increasing to ∼ 22 µmol N kg −1 at the oxic-anoxic interface ([O 2 ] < ∼ 4 µmol kg −1 , ∼ 250 m). Below the oxicanoxic interface (300-400 m), the average concentration of N xs 2 was 24.7 ± 1.9 µmol N kg −1 in September 2008 and 27.5 ± 2.0 µmol N kg −1 in March 2009, i.e., N xs 2 concentrations within this depth interval were ∼ 3 µmol N kg −1 higher (p < 0.001) during the upwelling season compared to the non-upwelling period. These results suggest that Nloss in the Cariaco Basin may vary seasonally in response to changes in the flux of sinking particulate organic matter. We attribute the increase in N xs 2 concentrations, or N-loss, observed during upwelling to: (1) higher availability of fixed nitrogen derived from suspended and sinking particles at the oxic-anoxic interface and/or (2) enhanced ventilation at the oxic-anoxic interface during upwelling.

show abstract

Close coupling of N‐cycling processes expressed in stable isotope data at the redoxcline of the Baltic Sea

Frey

Dippner

Voß

2014

Global Biogeochemical Cycles

View full text Add to dashboard Cite

Over the past decades, the hypoxic state of the central Baltic Sea has deteriorated because of eutrophication, but little is known about the extent to which related factors such as nitrogen removal have been altered. The Baltic Sea is a stratified semi-enclosed basin with a large, anoxic bottom water mass in its central Gotland Basin and highly active microbial nitrogen transformation processes at the redoxcline, the interface between oxic and anoxic waters. In this study, we identified and quantified the dominant transformation processes of reactive nitrogen by exploiting fine resolution profiles of δ 15 N NO3 , δ 18 O NO3 , and δ 15 N NH4 through the pelagic redoxcline between 60 and 140 m. Our results showed increasing δ 15 N NO3 and δ 18 O NO3 values with decreasing nitrate concentrations, but the associated low apparent isotope effect (ε =~5‰), as inferred from a closed system Rayleigh model, was not consistent with the high ε (~25‰) characteristic of denitrification in the water column. These findings could be explained by substrate limitation. The observed δ 18 O NO3 :δ 15 N NO3 ratio of 1.38:1 rather than the usual 1:1 ratio typical for denitrification-dominated systems could be explained by the occurrence of both nitrification and denitrification. We then developed a numeric reaction-diffusion model, according to which a realistic denitrification rate of 14 nmol N L À1 d À1 was estimated, and a nitrification rate of 6.6 nmol N L À1 d À1 confirmed. Our study not only demonstrates the value of stable isotope data for investigating nitrogen transformation processes but also highlights that care is needed in interpreting systems with closely coupled processes such as those at ocean redoxclines.

show abstract

Concentration and natural stable isotope profiles of nitrogen species in theBlack Sea

Cited by 79 publications

References 59 publications

The evolution of Earth's biogeochemical nitrogen cycle

The evolution of Earth's biogeochemical nitrogen cycle

Biogenic nitrogen gas production at the oxic–anoxic interface in the Cariaco Basin, Venezuela

Close coupling of N‐cycling processes expressed in stable isotope data at the redoxcline of the Baltic Sea

Contact Info

Product

Resources

About