Assessment of Oceanic Productivity with the Triple-Isotope Composition of Dissolved Oxygen

Luz, Boaz; Barkan, Eugeni

doi:10.1126/science.288.5473.2028

Cited by 230 publications

(412 citation statements)

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“…The correction for ␦ 18 O can be calculated in a similar way; on average, it was ϳ0.02‰. The isotopic and elemental ratios are reported with respect to an air standard-HLA (Luz and Barkan 2000). The integrity of the standard was checked every month by measuring samples of outside air.…”

Section: Field and Laboratory Methodsmentioning

confidence: 99%

“…After equilibration, the water was sucked out of the flasks leaving only headspace gases. The flasks were then connected to a preparation system for the purification of O 2 and Ar (Luz et al 1999). After purification, the O 2 -Ar mixture was transferred to stainless steel holding tubes for further mass spectrometric measurements.…”

Section: Field and Laboratory Methodsmentioning

confidence: 99%

“…The main drawback of these methods is their inability to measure the rate of O 2 uptake in the light, and it is unavoidably assumed that the rates of dark and light uptakes are equal. The rates of gross production as well as light O 2 uptake can be estimated in field incubation experiments using H 2 18 O as a spike (e.g., Bender et al 1987Bender et al , 1999Luz and Barkan 2000). However, this method alone cannot help to characterize the type of the respiratory mechanisms involved in aquatic O 2 uptake.…”

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confidence: 99%

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Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Luz

Barkan

Sagi

et al. 2002

Limnology & Oceanography

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125

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Gross and net O 2 production between May 1996 and February 1999 was determined in bottle incubation experiments with H 2 18 O spike and from the change in O 2 concentration. Carbon fixation rates were obtained from 14 C incubations. In general, production rates determined using the H 2 18 O-spike were about twice the primary production determined by the 14 C method, where the latter was close to net oxygen evolution. These relationships are similar to results for the open ocean. During the spring bloom, when the dinoflagellate Peridinium was abundant, the ratio of gross O 2 production to carbon fixation was about 7.5, and net O 2 production was greater than carbon fixation. The difference between O 2 gross production and carbon fixation results, at least in part, from uptake by Mehler reaction and from recycling of the 14 C tracer by dark respiration and the alternative oxidase (AOX). We used the difference in isotopic discrimination against 18 O, occurring during O 2 consumption by various biological pathways, to place constraints on the relative engagement of these pathways. We estimated the overall discrimination against 18 O in the lake from O 2 isotopic mass balance as 20.5-29‰. The only mechanism that can explain the strong overall fractionation in the lake is AOX, which strongly discriminates against 18 O (ϳ31‰). Our results show, for the first time, that uptake by AOX is widespread and quantitatively important to oxygen consumption in aquatic systems.Oxygen exchange by photosynthesis and respiration is the largest biogeochemical cycle in aquatic systems. In order to understand this cycle, it is necessary to know the gross rates of the major processes involved in oxygen production and uptake. Production of O 2 is known to occur in one process in photosystem II, but O 2 consumption in aquatic organisms is possible by several reactions. These include ordinary respiration through the cytochrome oxidase pathway, respiration by the alternative oxidase pathway, Mehler reaction, and photorespiration. The first two processes take place in light as well as in dark conditions, whereas the latter two occur only under illumination. Although the presence of the above mechanisms has been established in different studies, their quantitative importance in the overall O 2 uptake in aquatic systems is not well known, and it is necessary to assess their role in natural environments. In this respect, ordinary O 2 incubation methods, which are very useful for the assessment of photosynthetic production from light-and dark-incubation experiments (e.g., Williams and Purdie 1991), do not provide the necessary information. The main drawback of these methods is their inability to measure the rate of O 2 AcknowledgmentsWe thank Y. Geiffman and the Mekorot Watershed Unit for provision of wind data and extend special thanks to the Kinneret Limnological Laboratory skipper M. Hatab. We are grateful

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Section: Field and Laboratory Methodsmentioning

confidence: 99%

Section: Field and Laboratory Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Luz

Barkan

Sagi

et al. 2002

Limnology & Oceanography

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125

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“…[10] The oxygen atom in N 2 O produced by these sources most likely derives from atmospheric O 2 , which is depleted in 17 O by À0.25% relative to the meteoric water line [Luz and Barkan, 2000]. This source therefore diminishes the isotope anomaly of atmospheric N 2 O slightly.…”

Section: Biomass Burning and Industrial Processesmentioning

confidence: 99%

Absence of isotope exchange in the reaction of N₂O + O(¹D) and the global Δ¹⁷O budget of nitrous oxide

Kaiser

Röckmann

2005

Geophysical Research Letters

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“…The export of carbon by the biological pump is conventionally regarded to be constrained by the nitrogen input, which is believed to set an upper limit to the organic carbon export equal to the product of the C/N ratio in the export organic carbon and the nitrogen supplied to the biogenic layer (Ducklow 1995;Williams 1995;Field et al 1998). The nitrogen input to the photic zone of the ocean is mainly derived from the internal supply of nitrate through vertical mixing, estimated at ∼50 Tmol N a −1 in subtropical waters (Jenkins and Wallace 1992;Lewis 2002), atmospheric inputs (Ducklow 1995;Williams 1995;Field et al 1998;Luz and Barkan 2000), estimated at about 10 Tmol N a −1 (Longhurst et al 1995) and nitrogen fixation for which there is little consensus on the global rate (7-14 Tmol N a −1 ; Karl et al 2002). The assumption that this net production equals the net carbon export by the biological pump is, in turn, based on the assumption that the carbon and nitrogen transport in the upward inorganic and the downward organic fluxes are in similar stoichiometric balance, but the latter assumption is unsupported by current data.…”

Section: Overall Rates Of Export Of Organic Carbon From the Photic Layermentioning

confidence: 99%

Respiration in the mesopelagic and bathypelagic zones of the oceans

Arı́stegui¹,

Agustı́²,

Middelburg³

et al. 2005

Respiration in Aquatic Ecosystems

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OutlineIn this chapter the mechanisms of transport and remineralization of organic matter in the dark water-column and sediments of the oceans are reviewed. We compare the different approaches to estimate respiration rates, and discuss the discrepancies obtained by the different methodologies. Finally, a respiratory carbon budget is produced for the dark ocean, which includes vertical and lateral fluxes of organic matter. In spite of the uncertainties inherent in the different approaches to estimate carbon fluxes and oxygen consumption in the dark ocean, estimates vary only by a factor of 1.5. Overall, direct measurements of respiration, as well as indirect approaches, converge to suggest a total dark ocean respiration of 1.5-1.7 Pmol C a −1 . Carbon mass balances in the dark ocean suggest that the dark ocean receives 1.5-1.6 Pmol C a −1 , similar to the estimated respiration, of which >70% is in the form of sinking particles. Almost all the organic matter (∼92%) is remineralized in the water column, the burial in sediments accounts for <1%. Mesopelagic (150-1000 m) respiration accounts for ∼70% of dark ocean respiration, with average integrated rates of 3-4 mol C m −2 a −1 , 6-8 times greater than in the bathypelagic zone (∼0.5 mol C m −2 a −1 ). The results presented here renders respiration in the dark ocean a major component of the carbon flux in the biosphere, and should promote research in the dark ocean, with the aim of better constraining the role of the biological pump in the removal and storage of atmospheric carbon dioxide.

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Assessment of Oceanic Productivity with the Triple-Isotope Composition of Dissolved Oxygen

Cited by 230 publications

References 24 publications

Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Absence of isotope exchange in the reaction of N₂O + O(¹D) and the global Δ¹⁷O budget of nitrous oxide

Respiration in the mesopelagic and bathypelagic zones of the oceans

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Assessment of Oceanic Productivity with the Triple-Isotope Composition of Dissolved Oxygen

Cited by 230 publications

References 24 publications

Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Absence of isotope exchange in the reaction of N2O + O(1D) and the global Δ17O budget of nitrous oxide

Respiration in the mesopelagic and bathypelagic zones of the oceans

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Absence of isotope exchange in the reaction of N₂O + O(¹D) and the global Δ¹⁷O budget of nitrous oxide