Linking biogeochemistry to hydro-geometrical variability in tidal estuaries: a generic modeling approach

Volta, Chiara; Laruelle, Goulven Gildas; Arndt, Sandra; Regnier, Pierre

doi:10.5194/hessd-12-6351-2015

Cited by 3 publications

(8 citation statements)

References 115 publications

(239 reference statements)

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“…The bulk of the remaining estimates falls in the 10%–50% range, which is consistent with our results where estuarine systems characterized by short residence times of several days like small deltas only denitrify a few percent of TN in , while systems such as fjords with residence times of several years denitrify up to 38% of TN in . Our results are also in line with the study of Volta, Laruelle, Arndt, and Regnier () who used a generic, physically based estuarine modeling approach spanning a wide range of estuarine geometries; these authors report mean N losses via denitrification in the range 15%–25%.…”

Section: Resultssupporting

confidence: 91%

Nitrous oxide emissions from inland waters: Are IPCC estimates too high?

Maavara

Lauerwald

Laruelle

et al. 2018

Global Change Biology

164

197

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Nitrous oxide (N2O) emissions from inland waters remain a major source of uncertainty in global greenhouse gas budgets. N2O emissions are typically estimated using emission factors (EFs), defined as the proportion of the terrestrial nitrogen (N) load to a water body that is emitted as N2O to the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) has proposed EFs of 0.25% and 0.75%, though studies have suggested that both these values are either too high or too low. In this work, we develop a mechanistic modeling approach to explicitly predict N2O production and emissions via nitrification and denitrification in rivers, reservoirs and estuaries. In particular, we introduce a water residence time dependence, which kinetically limits the extent of denitrification and nitrification in water bodies. We revise existing spatially explicit estimates of N loads to inland waters to predict both lumped watershed and half‐degree grid cell emissions and EFs worldwide, as well as the proportions of these emissions that originate from denitrification and nitrification. We estimate global inland water N2O emissions of 10.6–19.8 Gmol N year−1 (148–277 Gg N year−1), with reservoirs producing most N2O per unit area. Our results indicate that IPCC EFs are likely overestimated by up to an order of magnitude, and that achieving the magnitude of the IPCC's EFs is kinetically improbable in most river systems. Denitrification represents the major pathway of N2O production in river systems, whereas nitrification dominates production in reservoirs and estuaries.

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Section: Resultssupporting

confidence: 91%

Nitrous oxide emissions from inland waters: Are IPCC estimates too high?

Maavara

Lauerwald

Laruelle

et al. 2018

Global Change Biology

164

197

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“…It uses idealized geometry (defined by the estuarine width at the mouth, convergence length, and channel depth profile; see Volta et al, 2014, for details) and hydrodynamics (such as river discharge and tidal amplitude) that can be gained from remote sensing images using Geographic Information Software (GIS) and readily available data sets (Table 1). The biogeochemical reaction network includes SPM settling and erosion, the air-water gas exchange for oxygen (O 2 ) and carbon dioxide (CO 2 ), nitrification, denitrification, primary production, phytoplankton mortality, and the aerobic degradation of organic matter (see the Supplement for detailed descriptions and mathematical formulations, according to Volta et al, 2014Volta et al, , 2016a. Essential state variables are used in the simulations, as are those gathered above (as mentioned in Sect.…”

Section: Model Description and Setupmentioning

confidence: 99%

“…The same set of values for all biogeochemical parameters was used for all of the selected estuaries (Table 6). On the whole, only slight variations from the parameterization in Laruelle et al (2019) were required, ensuring that all parameters remained within a range corresponding to values representative of temperate estuaries, following the extensive literature survey carried out by Volta et al (2016a).…”

Section: Model Calibrationmentioning

confidence: 99%

“…The generic implementation of the C-GEM model relies on a limited amount of basic information to describe estuarine geometry, hydrodynamic information, and the inputs to estuaries, and then produces annual to multidecadal simulations. C-GEM has already been applied to one tropical estuary (Nguyen et al, 2021) and several temperate estuaries and has provided satisfactory simulations of nutrient transport and biogeochemical processes despite the simplification of the estuarine geometry (Laruelle et al, 2017(Laruelle et al, , 2019Volta et al, 2014Volta et al, , 2016a). An extensive description of C-GEM is presented in Volta et al (2014Volta et al ( , 2016a.…”

Section: Introductionmentioning

confidence: 99%

“…C-GEM has already been applied to one tropical estuary (Nguyen et al, 2021) and several temperate estuaries and has provided satisfactory simulations of nutrient transport and biogeochemical processes despite the simplification of the estuarine geometry (Laruelle et al, 2017(Laruelle et al, , 2019Volta et al, 2014Volta et al, , 2016a). An extensive description of C-GEM is presented in Volta et al (2014Volta et al ( , 2016a.…”

Section: Introductionmentioning

confidence: 99%

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Nutrient transport and transformation in macrotidal estuaries of the French Atlantic coast: a modeling approach using the Carbon-Generic Estuarine Model

Garnier

Thieu

et al. 2022

Biogeosciences

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Abstract. Estuaries are key reactive ecosystems along the land–ocean aquatic continuum, with significant ecological and economic value. However, they have been facing strong morphological management changes and increased nutrient and contaminant inputs, possibly leading to ecological problems such as coastal eutrophication. Therefore, it is necessary to quantify the import and export fluxes of the estuaries, their retention capacity, and estuarine eutrophication potential. The 1-D Carbon-Generic Estuary Model (C-GEM) was used to simulate the transient hydrodynamics, transport, and biogeochemistry for estuaries with different sizes and morphologies along the French Atlantic coast during the period 2014–2016 using readily available geometric, hydraulic, and biogeochemical data. These simulations allowed us to evaluate the budgets of the main nutrients (phosphorus – P; nitrogen – N; silica – Si) and total organic carbon (TOC), and their imbalance, providing insights into their eutrophication potential. Cumulated average annual fluxes to the Atlantic coast from the seven estuaries studied were 9.6 kt P yr−1, 259 kt N yr−1, 304 kt Si yr−1, and 145 kt C yr−1. Retention rates varied depending on the estuarine residence times, ranging from 0 %–27 % and 0 %–34 % to 2 %–39 % and 8 %–96 % for total phosphorus (TP), total nitrogen (TN), dissolved silica (DSi), and TOC, respectively. Large-scale estuaries had higher retention rates than medium and small estuaries, which we interpreted in terms of estuarine residence times. As shown by the indicator of eutrophication potential (ICEP), there might be a risk of coastal eutrophication, i.e., the development of non-siliceous algae that is potentially harmful to the systems studied due to the excess TN over DSi. This study also demonstrates the ability of our model to be applied with a similar setup to several estuarine systems characterized by different sizes, geometries, and riverine loads.

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