Deep Sea Research and Oceanographic Abstracts, 1971
Unusually high oxygen concentrations (sometimes greater than 150 % of saturation values) are ofte... more Unusually high oxygen concentrations (sometimes greater than 150 % of saturation values) are often observed in the Chukchi and East Siberian seas between Bering Strait and approximately 170°E. These high concentrations appear to arise primarily from in situ photosynthetic production. The highest concentrations were observed in stratified waters that probably left the surface in winter when the water was nearly saturated with air and contained high nutrient concentrations. These highly oxygenated strata generally were separated from the surface by shallow pycnoclines. High oxygen concentrations have also been observed in the relatively warm waters of the Bering Strait inflow. Nutrient enrichment of the surface layers by turbulence in the Strait may contribute to these high concentrations.
Oceanic depth profiles of plankton respiration are described by a power function, R CO 2 = (R CO ... more Oceanic depth profiles of plankton respiration are described by a power function, R CO 2 = (R CO 2) 0 (z/z 0) b , similar to the vertical carbon flux profile. Furthermore, because both ocean processes are closely related, conceptually and mathematically, each can be calculated from the other. The exponent b, always negative, defines the maximum curvature of the respiration-depth profile and controls the carbon flux. When |b| is large, the carbon flux (F C) from the epipelagic ocean is low and the nutrient retention efficiency (NRE) is high, allowing these waters to maintain high productivity. The opposite occurs when |b| is small. This means that the attenuation of respiration in ocean water columns is critical in understanding and predicting both vertical F C as well as the capacity of epipelagic ecosystems to retain their nutrients. The ratio of seawater R CO 2 to incoming F C is the NRE, a new metric that represents nutrient regeneration in a seawater layer in reference to the nutrients introduced into that layer via F C. A depth profile of F C is the integral of water column respiration. This relationship facilitates calculating ocean sections of F C from water column respiration. In an F C section and in a NRE section across the Peruvian upwelling system we found an F C maximum and a NRE minimum extending down to 400 m, 50 km off the Peruvian coast over the upper part of the continental slope. Finally, considering the coupling between respiratory electron transport system activity and heterotrophic oxidative phosphorylation promoted the calculation of an ocean section of het-erotrophic energy production (HEP). It ranged from 250 to 500 J d −1 m −3 in the euphotic zone to less than 5 J d −1 m −3 below 200 m on this ocean section.
A nitrification-denitrification couple that may be summarized by the pathway, NH~-+ N20-* N2 has ... more A nitrification-denitrification couple that may be summarized by the pathway, NH~-+ N20-* N2 has not been included in past studies of marine denitrification. Neglect of this pathway could lead to underestimates of the amounts of free nitrogen produced by denitrification. Because of this and because our analysis suggests that loss of nitrite from oxygen-deficient waters found in the eastern tropical South Pacific does not introduce major errors, we suggest a total denitrification rate of ~ 60 Tg N y-1 for the marine water column. Recent studies of the sedimentary denitrification rate also suggest a value of ~" 60 Tg N y-1 while estimates for the combined nitrogen inputs into the sea via the atmosphere and marine nitrogen fixation have decreased. These findings suggest an unbalanced marine combined-nitrogen budget in which the removal rate significantly exceeds the input. Consideration of the characteristics of nitrifying and denitrifying bacteria and of the distribution of variables in the eastern tropical South Pacific suggest high N20 turnover rates in eastern boundary regions. Since N20 may he produced at extremely high rates at the boundary of oxygen-deficient (02 ~ ~ 0.1 ml 1:1) waters and consumed within these zones, whether the ocean is a source or sink for atmospheric N20 may depend critically on the exact nature of the dissolved oxygen distribution.
Deep Sea Research Part II: Topical Studies in Oceanography, 2005
As part of the Western Arctic Shelf-Basin Interactions (SBI) project, the production and fate of ... more As part of the Western Arctic Shelf-Basin Interactions (SBI) project, the production and fate of organic carbon and nitrogen from the Chukchi and Beaufort Sea shelves were investigated during spring (5 May-15 June) and summer (15 July-25 August) cruises in 2002. Seasonal observations of suspended particulate organic carbon (POC) and nitrogen (PON) and large-particle (453 mm) size class suggest that there was a large accumulation of carbon (C) and nitrogen (N) between spring and summer in the surface mixed layer due to high phytoplankton productivity. Considerable organic matter appeared to be transported from the shelf into the Arctic Ocean basin in an elevated POC and PON layer at the top of the upper halocline. Seasonal changes in the molar carbon:nitrogen (C:N) ratio of the suspended particulate organic matter (POM) pool reflect a change in the quality of the organic material that was present and presumably being exported to the sediment and to Arctic Ocean waters adjacent to the Chukchi and Beaufort Sea shelves. In spring, low particulate C:N ratios (o6; i.e., N rich) were observed in nitrate-replete surface waters. By the summer, localized high particulate C:N ratios (49; i.e., N-poor) were observed in nitrate-depleted surface waters. Low POC and inorganic nutrient concentrations observed in the surface layer suggest that rates of primary, new and export production are low in the Canada Basin region of the Arctic Ocean.
Deep Sea Research Part I: Oceanographic Research Papers, 2007
Determinations of the activity of the respiratory electron transport system (ETS), during the FRA... more Determinations of the activity of the respiratory electron transport system (ETS), during the FRAM III expedition permit us to estimate oxygen utilization rates (R O 2) from the surface to 2000 m under the polar pack ice in the Nansen Basin just north of Svalbard (831N, 71E) during April 1981. We found R O 2 at in situ temperatures ranging from 20 pM O 2 min À1 just below the ice to 0.2 pM O 2 min À1 at 2000 m. These rates are low compared to most other ocean regions, but they could decrease particulate organic carbon and nitrogen by 76% and 74%, respectively, over a period of $6 months. The R O 2 calculations based on measurements made at 0 1C yielded a power function of R O 2 vs. depth (Z) of R O 2 ¼ 67Z À0.5534. When this R O 2 profile was superimposed on a more recent oxygen utilization rate profile made using the 3 He-3 H-AOU method (OUR), in the same
Deep Sea Research Part A. Oceanographic Research Papers, 1980
The distribution of suspended particulate matter was measured during 21 May and 18 June 1977 betw... more The distribution of suspended particulate matter was measured during 21 May and 18 June 1977 between 4 and 23°S from the coast of South America to about 500 nautical miles offshore. A well-defined maximum was observed over the continental margins at depths of about 200 m between ~ 9 and 23°S. At 4°S, the main particle maximum was at approximately 400 m, but in the nearshore zone the maximum extended upwards to ~ 200 m. A comparison of the particle and chemical data shows that the particle maxima are usually at approximately the core depth of the oxygen minimum layer. A nitrite maximum and a nitrate minimum were also observed at or near the particle maximum core depth south of ~ 9°S. Near 4°S, a weak nitrite maximum was observed within the oxygen minimum layer at some stations. The protein distribution near 15°S suggests that the material in the particle maximum contains significant amounts of organic matter. The distribution of the particle maximum layer between 9 and 23°S and its relations to the density field and the cross-shelf flow suggest that most of the particles could originate in the bottom waters over the outer continental shelf and be transported offshore in a quasi-horizontal path. Offshore particle transport near the equator is probably supported by a westward current off northern Peru between and under the eastward extension of the Equatorial Undercurrent and the Subsurface South Equatorial Countercurrent. However, the source of the particles in this ~ 400-m maximum has not been determined.
The dominant factors influencing the micronutrient distributions observed in the East Siberian an... more The dominant factors influencing the micronutrient distributions observed in the East Siberian and Laptev seas during the summer of 1963 appear to be the summer phytoplankton bloom, respiratory processes, the outflow of the Lena River, and the different origins of the high-salinity waters found in the two seas. RÉSUMÉ. Distribution des microéléments nutritifs dans la mer de Sibérie orientale et dans la mer de Laptev au cours de l'été 1963. L'éclosion estivale du plancton, les processus respiratoires, la décharge du fleuve Léna et les origines diverses des eaux de haute salinité semblent être les facteurs dominants qui influencent la distribution des microéléments nutritifs observée dans la mer de Sibérie orientale et dans la mer de Laptev.
Deep Sea Research Part A. Oceanographic Research Papers, 1989
Simultaneous optical, biological and chemical analyses of coastal waters off Peru were made durin... more Simultaneous optical, biological and chemical analyses of coastal waters off Peru were made during a period characterized by anomalously cold surface waters and weak wind-driven coastal upwelling. Particle size distributions and the microbial and chemical nature of the intermediate nepheloid layers provide strong evidence that bacterial growth, settling and offshore transport of particles are major processes controlling the particulate structure of the nearshore waters. The data also support previous suggestions that mid-depth maxima in suspended particles associated with nitrite maxima have a large bacterial component. Further, these results demonstrate the effectiveness of in situ optical methods for detection and quantification of the bacterial component of particle size distributions. While some features were similar to the particulate structures observed previously in Peruvian coastal waters, the data show the region to have significant temporal and spatial variability.
Comment #2: I may be misunderstanding the authors. To me the expression DOC-based respiration sta... more Comment #2: I may be misunderstanding the authors. To me the expression DOC-based respiration stands for the portion of R supported by DOC, rather than the amount of DOC drawdown by R. However, it seems that the focus in the response of the authors is on substantiating that the contribution of DOC to the vertical flux of TOC may be minor, which I agree. If I am correct, I would suggest to change the expression DOC-based R to DOC flux. I would also suggest to explicitly state in the manuscript that FC stands for particle C flux. However, DOC-based R (I mean the portion of R supported by DOC) is included in the ETS measurement, hence I would say that rather than assuming that DOC flux is negligible, the calculated FC would be total rather than POC only. Comment #3: My concern is not for the scale of the measurement of R, but for the assumption of steady-state implicit in the calculation of FC from " instantaneous" R in a water column of up to 2000 m depth. In my opinion this...
Deep Sea Research Part A. Oceanographic Research Papers, 1990
Rates of transformations of inorganic nitrogen were measured in the low oxygen, subsurface waters... more Rates of transformations of inorganic nitrogen were measured in the low oxygen, subsurface waters (50--450 m) of the Eastern Tropical South Pacific during February 1985, using 15N tracer techniques. Oxygen concentrations over the entire region were in a range (O 2 < 2.5/aM) that allowed both oxidation and reduction of nitrogen to occur. A wide range of rates was observed for the lowest oxygen levels, indicating that observed oxygen concentration was not a primary factor regulating nitrogen metabolism. High values for subsurface metabolic rates correspond with high levels for surface primary production, both apparently associated with mesoscale features observed in satellite imagery and with mesoscale features of the current field. Measured rates of nitrate reduction and estimated rates of denitrification were sufficient to respire nearly all of the surface primary production that might be transported into the oxygendeficient zone. These results imply that the supply of labile organic material, especially from the surface, was more important than oxygen concentration in modulating the rates of nitrogen transformations within the low oxygen water mass of the Eastern Tropical South Pacific. The pattern of nitrite oxidation and nitrate reduction activities in the oxygen minimum zone supports the hypothesis (ANDEaSON et al., 1982, Deep-Sea Research. 29, 1113-1140) that nitrite, produced from nitrate reduction, can be recycled by oxidation at the interface between low and high oxygen waters. Rates for denitrification, estimated from nitrate reduction rates, were in harmony with prcvious estimates based on electron transport systcm (ETS) measurements and analysis of the nitrate deficit and water residence times. Assimilation rates of NH~" were substantial, providing evidence for heterotrophic bacterial growth in low oxygen waters. Ambient concentrations of ammonium were maintained at low values primarily by assimilation: ammonium oxidation was an important mechanism at the surface boundary of the low oxygen zone.
An oceanic fixed nitrogen sink exceeding 400 Tg N a?1 vs the concept of homeostasis in the fixed-... more An oceanic fixed nitrogen sink exceeding 400 Tg N a?1 vs the concept of homeostasis in the fixed-nitrogen inventory L. A. Codispoti To cite this version: L. A. Codispoti. An oceanic fixed nitrogen sink exceeding 400 Tg N a?1 vs the concept of homeostasis in the fixed-nitrogen inventory. Biogeosciences Discussions, European Geosciences
Budgetary and biogeochemical implications of N2O isotope signatures in the Arabian Sea
Nature
Nitrous oxide (N2O) is an important greenhouse gas that also plays a role in the chemistry of str... more Nitrous oxide (N2O) is an important greenhouse gas that also plays a role in the chemistry of stratospheric ozone depletion, but its atmospheric budget has yet to be well-quantified. However, multi-isotope characterization of N2O emitted from various natural sources is a potentially powerful tool for providing the much-needed constraints. It is generally believed that production of isotopically light (low 15N/14N and 18O/16O ratios) N2O occurs in the upper ocean through nitrification process, and that the flux of this light N2O from sea to air isotopically counters the flux of heavy N2O from the stratosphere to the troposphere,. But eastern-boundary ocean-upwelling zones, which contain oxygen-depleted waters and are sites of intense N2O efflux, have not been adequately studied. We show here, using new isotope data, that in spite of huge denitrification-related enrichments of 15N and 18O in N2O at mid-depths in the Arabian Sea, N2O emitted from upwelled waters is only slightly enriched in 18O, and moderately depleted in 15N, relative to air. These opposing isotopic signatures and modest departures from the isotopic composition of tropospheric N2O indicate that air-sea exchange cannot - given the heavy isotopic signature of N2O derived from the stratosphere - allow the tropospheric budget of N2O to be closed without invoking hitherto-unknown N2O sources and sinks. Our oceanic data cannot be explained through either nitrification or denitrification alone, such that a coupling between the two processes may be an important mechanism of N2O production.
On the fourteenth of March 1981, Fram 3, the third in a series of four U.S. manned ice camps, was... more On the fourteenth of March 1981, Fram 3, the third in a series of four U.S. manned ice camps, was established in the eastern Arctic Ocean at 84.32°N, 20.07°E for oceanographic and geophysical research in the Eurasian Basin north of the Greenland-Spitzbergen Passage.Investigators from several institutions in the United States, as well as from Canada and England, participated in studies
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