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Fraga, Fernando; Rı́os, Aida F.; Pérez, Fíz F.; Figueiras, Francisco G.

doi:10.3989/scimar.1998.62n1-2161

Cited by 57 publications

(10 citation statements)

References 30 publications

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“…), and the ratio between the change in total alkalinity and nitrogen (r AT:N ) as well. The ranges of variation for the ratios were within the theoretical limits of marine organic matter composition (Fraga et al, 1998). Although the model does show a sensitivity to the ratios (Fig.…”

Section: Modifying the Stoichiometric Ratiossupporting

confidence: 69%

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Long-term integrated biogeochemical budget driven by circulation in the eastern subpolar North Atlantic

Fontela

Mercier

Pérez

2019

Progress in Oceanography

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The eastern subpolar North Atlantic (eSPNA) is a key region in the Atlantic Meridional Overturning Circulation (AMOC), playing an important role in biogeochemical cycles and climate regulation. Quantitative basin-scale biogeochemical budgets are still scarce despite the current need of establishing baselines of knowledge in a changing ocean. The physico-chemical data from the eight repetitions of the OVIDE section (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) are an unique opportunity to develop a novel evaluation of biogeochemical budgets in the eSPNA by combining robust and well established decadal mean mass transports with carbon variables, oxygen and inorganic nutrients in a full-depth inverse box model. The net balance between the carbon fixation and the respiration throughout the whole water column shows that the eSPNA is an important dissolved inorganic carbon (DIC) sink area where 119 ± 43 kmol·s-1 and 49 ± 31 kmol·s-1 of organic and inorganic carbon, respectively, are currently exported. The uptake due to mixed layer depth oxygenation of 807 ± 114 kmol·s-1 of oxygen from the atmosphere and its subsequent southward export are responsible for deep Atlantic Ocean oxygenation. Deep water formation processes connect the northward upper limb with the southward lower limb of the AMOC leading to tracer export to the deep ocean. With regard to the net macronutrient budgets, all element consumptions are balanced within uncertainties. The results presented here for carbon export and oxygen uptake are in agreement with the upper range of previous observations based on different methods. The findings of this integrated budget driven by circulation in the highly dynamic region of the eSPNA can be taken as a reference in future biogeochemical evaluations of the North Atlantic. Highlights► A large DIC sink due the biological pump is quantified in the eSPNA. ► The eSPNA is an autotrophic area of DIC sink (168±53 kmol·s -1 ) and oxygen uptake. ► Whole-water column biogeochemical budgets are based on 14 years of observations. ► Budgets of elements C, O, N, P and Si are consistently integrated and optimized.

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Section: Modifying the Stoichiometric Ratiossupporting

confidence: 69%

“…3). Regardless, taken into account the theoretical limits of elemental composition (Fraga et al, 1998), the output for the sinks are within the range of the uncertainties on the biogeochemical estimates optimized by the model.…”

Section: Discussionmentioning

confidence: 88%

Long-term integrated biogeochemical budget driven by circulation in the eastern subpolar North Atlantic

Fontela

Mercier

Pérez

2019

Progress in Oceanography

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“…Note that, as a consequence of the power relationship between the utilization rate constants (Figure 8 and Table 1) the isolines of the C: N: P stoichiometry of BDOM utilization (color background) were not parallel to the isolines of the percentage of unused BDOC (solid black lines) ( Figure 9). Initially, the substrates are utilized at very low C: N molar ratios, close to 4, which would be compatible with the preferential utilization of amino acids and/or nucleotides with average biochemical composition of C 138 H 127 O 45 N 39 S and C 45 H 76 O 31 N 12 P 5 respectively in marine phytoplankton [Anderson, 1995;Fraga et al, 1998]. The C: N utilization molar ratio increases up to 40 after an incubation period of 20 days at a rate of 0.15 day À1 .…”

Section: Dom Utilization Rates In the Coastal Oceanmentioning

confidence: 99%

Recycling versus export of bioavailable dissolved organic matter in the coastal ocean and efficiency of the continental shelf pump

Lønborg

Álvarez‐Salgado

2012

Global Biogeochemical Cycles

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[1] At least 15% of the 2 Pg y À1 of dissolved organic carbon (DOC) that accumulates in the surface layer of the open ocean has been exported from the ocean margins. The C: N: P stoichiometry of the production and microbial degradation of dissolved organic matter (DOM) in the coastal ocean conditions the quality of the exported substrates. In this work, DOC, dissolved organic nitrogen (DON) and phosphorus (DOP) bioavailability measurements from published bottle incubation experiments have been compiled and reanalyzed to examine the role of bioavailable DOM (BDOM) in the coastal ocean. DOM bioavailability decreased significantly (p < 0.001) in the sequence DOP > DON > DOC, with bioavailable DOC (BDOC) representing 22 AE 12% (mean AE SD) of the total DOC, bioavailable DON (BDON) 35 AE 13% of the total DON and bioavailable DOP (BDOP) 70 AE 18% of the total DOP. This suggests that the role of DOM on the recycled and export production of the coastal ocean is more relevant for the P than for the N and for the N than for the C biogeochemical cycles. First-order microbial degradation rate constants (k) of BDOM (normalized to 15 C) increased significantly (p < 0.05) in the same sequence, with k C being 0.066 AE 0.065 day À1 , k N 0.111 AE 0.096 and k P 0.154 AE 0.137 day À1 . Significant (p < 0.001) power relationships were found among k C , k N and k P (R 2 = 0.84-0.87). The C: N: P molar ratio of the DOM that resists microbial degradation was extremely depleted in N and P, 2835 (AE3383): 159 (AE187): 1, compared with the BDOM fraction, 197 (AE111): 25 (AE16): 1. The flushing time (t) of the coastal ocean in relation to the turnover time of BDOM (1/k), i.e., t Á k, dictates the fate -degradation versus accumulation-of the large scale export of BDOM, which could fuel parts of the oceanic new production and influence the N/P limitation of the open ocean.Citation: Lønborg, C., and X. A. Álvarez-Salgado (2012), Recycling versus export of bioavailable dissolved organic matter in the coastal ocean and efficiency of the continental shelf pump, Global Biogeochem. Cycles, 26, GB3018,

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“…S1, e.g. Redfield et al 1963;Fraga et al 1998;Middelburg and Herman 2007). Towards the MTZ, C/N values, PN and PC contents decreased, indicating remineralization in the water column.…”

Section: Dissolved Oxygen Saturationmentioning

confidence: 98%

Seasonal variability of nitrous oxide concentrations and emissions along the Elbe estuary

Schulz

Sanders

Voynova

et al. 2023

Preprint

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Abstract. Nitrous oxide (N2O) is a greenhouse gas, with a global warming potential 298 times that of carbon dioxide. Estuaries can be sources of N2O, but their emission estimates have significant uncertainties due to limited data availability and high spatiotemporal variability. We investigated the spatial and seasonal variability of dissolved N2O and N2O emissions along the Elbe estuary (Germany). During nine research cruises done between 2017 and 2022, we measured dissolved N2O concentrations, as well as dissolved nutrients and oxygen concentrations along the estuary and calculated N2O saturation, flux densities and emissions. We found intense N2O production along the Elbe estuary that compensated the effect of decreasing dissolved inorganic nitrogen (DIN) loads since the 1990s. Two hot-spots areas of N2O production have been identified in the estuary: the Port of Hamburg and the mesohaline estuary near the estuarine turbidity maximum (MTZ). N2O production was enhanced by warmer temperatures and fueled by riverine organic matter in the Hamburg Port or marine organic matter in the MTZ. Surprisingly, estuarine N2O emissions where equally high in winter and summer. In winter, high riverine N2O concentrations led to high N2O emissions from the estuary, whereas in summer, estuarine biological N2O production led to equally high N2O emissions. Overall, we find that the Elbe estuary is a year-round source of N2O with estimated annual emissions of 0.24 ± 0.06 Gg yr−1.

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Untitled

Cited by 57 publications

References 30 publications

Long-term integrated biogeochemical budget driven by circulation in the eastern subpolar North Atlantic

Long-term integrated biogeochemical budget driven by circulation in the eastern subpolar North Atlantic

Recycling versus export of bioavailable dissolved organic matter in the coastal ocean and efficiency of the continental shelf pump

Seasonal variability of nitrous oxide concentrations and emissions along the Elbe estuary

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